API Endpoint for SAML Group Sync

What does this MR do and why?

This MR resolves issue - #290367 (closed). We are introducing api endpoints to

1. get all the saml_group_links entries for a group
2. create an saml_group_link for a group
3. update an saml_group_link for a group

Screenshots or screen recordings

GET call -> /groups/<group_id>/

Added a new saml_group_link POST call -> /groups/<group_id>/saml_group_links

Newly added saml_group_link appeared in Get call for Groups API

Deleted the added group DELETE call -> /groups/<group_id>/saml_group_links/<saml_group_name>

Deleted saml_group_link no more appears in GET call GET call -> /groups/<group_id>/saml_group_links

How to set up and validate locally

Steps to setup

1. Install GDK and set up local development environment
2. Establish SAML authentication setup for a group GDK How to saml
3. Create a personal token and make note of it.
4. Use any API client or you can use curl commands also to test API calls .Personal token is mentioned in Authorization Header under heading PRIVATE TOKEN for user to get authorised

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.