# Subscribe to an Article

## Overview
The Subscribe to an Article API allows eGain users, authenticated customers and agents to subscribe and receive notifications about changes to an Article.

## Prerequisites
  * Notifications are sent only if the following conditions are met:
    * The Article content has been modified since the last published version.
    * The attachment list has been modified since the last published version.
    * The author has checked the "Include Article in new and modified Article list" option while publishing the Article.
  * For the Subscribe to an Article API to execute successfully:
    * The Article must be in the portal.
    * The user must have provided an email address.

## Permissions
  * Agent Permissions: The following permissions are required if the user is an agent:
    * If the Article has Access Tags:
      * The Article must be available for the agent's current user profile.
    * If the Article has Publish Views:
      * At least one edition of the Article must be available for the agent's current user profile.
    * If the Article has filters and the "tags query parameter" is provided:
      * The Article filters must match the provided tags or tag groups.
  * Customer Permissions: The following permissions are required if the user is a customer:
    * If the Article has Access Tags:
      * The portal must have a default user profile
      * The Article must be available for the portal's default user profile.
    * If the Article has Publish Views:
      * The portal must have a default user profile
      * At least one edition must be available for the portal's default user profile.
    * If the Article has filters and the "tags query parameter" is provided, then the Article filters must match the provided tags or tag groups.

Endpoint: PUT /portals/{portalID}/articles/{articleID}/subscribe
Security: oAuthUser, oAuthOnBehalfOfUser, oAuthCustomer, oAuthOnBehalfOfCustomer

## Header parameters:

  - `x-egain-activity-id` (string)
    A unique numeric interaction identifier from eGain.
    Example: "59237"

  - `x-ext-integration-id` (string)
    The unique numeric identifier for a tenant, used in self-service functionality as well as third-party integrations.Note: The x-ext-integration-id and x-ext-interaction-id headers must always be provided together and cannot be supplied independently.The x-egain-activity-id may be provided on its own, or it may be provided along with both x-ext-integration-id and x-ext-interaction-id.

  - `x-ext-interaction-id` (string)
    A unique interaction identifier from other CRM applications.Note: The x-ext-integration-id and x-ext-interaction-id headers must always be provided together and cannot be supplied independently.The x-egain-activity-id may be provided on its own, or it may be provided along with both x-ext-integration-id and x-ext-interaction-id.

  - `Accept-Language` (string, required)
    The Language locale accepted by the client (used for locale specific fields in resource representation and in error responses).
    Enum: "en-US", "es-ES", "fr-FR", "it-IT", "de-DE", "nl-NL", "pt-BR", "pt-PT", "da-DK", "ru-RU", "fr-CA", "zh-CN", "ja-JP", "ko-KR", "sv-SE"

## Path parameters:

  - `portalID` (string, required)
    The ID of the portal being accessed.A portal ID is composed of a 2-4 letter prefix, followed by a dash and 4-15 digits.
    Example: "PROD-1000"

  - `articleID` (string, required)
    The ID of the Article.An Article ID is composed of a 2-4 letter prefix followed by a dash and 4-15 digits.
    Example: "PROD-2996"

## Response 400 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.

## Response 401 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.

## Response 403 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.

## Response 404 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.

## Response 406 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.

## Response 500 fields (application/json):

  - `code` (string, required)
    A string that follows the pattern {integer}-{integer}.

The first {integer} is the http status code.  This code as a whole is unique.
* For example, error codes "400-101" and "404-101" are distinctly different.

  - `developerMessage` (string, required)
    A summary of the error.

  - `details` (array)

  - `details.key` (string, required)

  - `details.value` (string)

  - `userMessage` (string)
    UI friendly messages are only supported by some APIs.  
   The client must explicitly request UI friendly messages by passing the X-egain-error-message=yes* header.


## Response 204 fields