Adds one or more users as followers to the specified entity. Followers will receive notifications when the entity is updated,
commented on, or when its status changes. This operation requires appropriate permissions and validates all user
IDs before adding them.

Key Features:

• Validates all provided user IDs exist in the system before processing
• Supports bulk addition of multiple followers in a single request
• Returns complete follower information including user details
• Automatically converts user GUIDs to internal format for processing

Authorization Logic:

1. User must have a valid JWT token with appropriate scopes
2. User must have permission to manage the target entity
3. All follower user IDs must exist and be valid in the tenant

Usage Example:

Add team members as followers to receive updates about a critical program milestone.