BE: Create graphql API to return count of users in each roles

Why are we doing this work

Scan Result Policy Action currently supports individual approvers or a group of users. However, when a customer has projects with lower criticality or the scan results detect a vulnerability of low criticality (I.e., Low/Medium), they want to require an approver from the project based on the role (I.e., owner/maintainer)

This issue focusses on creating a graphql query Project.projectMembersCountByRole that returns the count of users in each role belonging to the project. This API can be used to show the count of users in each role.

Relevant links

• Epic: Support Role Based Approval Action for Scan Res... (&8018 - closed)

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

• backend Create Project.projectMembersCountByRole graphql field to ee/app/graphql/ee/types/project_type.rb that fetches the count of project_members for the given project by role

Verification steps