Allow to alter $admin_email and $params by using hook_alter

Problem/Motivation

Sometimes we need to add a recipient or change the text depending on the type of content or field values. We thought it could be done programmatically.

Proposed resolution

Allow to use hook_admin_content_notification_recipients_alter() and hook_admin_content_notification_params_alter().

Remaining tasks

None.

User interface changes

None.

API changes

Will be added admin_content_notification.api.php with instructions.

Data model changes

None.

Release notes snippet

Added hook_admin_content_notification_recipients_alter() and hook_admin_content_notification_params_alter().