Add Watcher

Adds a user as a watcher of an issue by passing the account ID of the user. For example, `"5b10ac8d82e05b22cc7d4ef5"`. If no user is specified the calling user is added.This operation requires the **Allow users to watch issues** option to be *ON*. This option is set in General configuration for Jira. See [Configuring Jira application options](https://confluence.atlassian.com/x/uYXKM) for details.**[Permissions](#permissions) required:** * *Browse projects* [project pe...