Merge invitations into domains service

[felixgateru]

@dborovcanin @felixgateru

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Merging the Invitation Service with the Domains Service

Reason for the Merge

Previously, the Invitation service relied on permissions aka roles (Admin, Editor, Viewer), along with the domain and invited user ID. However, we have now introduced a new structure where a role is defined by a set of actions/permissions and is uniquely identified by a role_id.

Given this change, When creating a new invitation , Invitation service now requires access to:

• role_id (to identify the assigned role, role_id resides in domains repo)
• domain_id (to associate the invitation with a domain)
• user_id (to identify the invited user)

Additionally, when listing invitations, we need to display the role name instead of just the role ID. This requires fetching role details from the Domains service.

Why Merge the Services?

• The Invitation service needs access to the Domains repository to retrieve role details (e.g., role name from role_id).
• Previously, Domains were part of the Auth service, but now Domains are an independent service.
• Since Invitations require domain-related data, merging the two services simplifies the architecture and removes the need for an external repository dependency.
• With this change, the invitation token becomes unnecessary, as invitation functions can directly access the required domain and role details.

Originally posted by @arvindh123 in #2435