F1: Implement and document /projects API

Description: Create /projects API to manage collaboration projects:

• GET /{project_id} returns {CollaborationProject} by ID
• PUT /{project_ID} body {CollaborationProject} returns updated {CollaborationProject}
• PATCH /{project_ID} body [{"op":"","path":"","value":""},...] returns patched {CollaborationProject}
• DELETE /{project_id} soft deletes {CollaborationProject} by ID

Acceptance criteria:

• Endpoints exist and responds with dummy (mocked) data.
• Endpoints present in the OpenAPI YAML
• Endpoints present in the OpenAPI /docs
• Endpoints' input/output CollaborationProject schema shown in the OpenAPI documentation
• All OpenAPI documentation is autogenerated from the API classes/codes descriptions.

Testing scenarios:

• As an API user I can get complete OpenAPI documentation about all API methods
  • as a rendered OpenAPI YAML document in the service repository on Gitlab
  • as a rendered OpenAPI YAML document by the deployed service's /docs endpoint
• As an API user I get expected (as documented by the OpenAPI documentation) response from any of API methods

Tech Notes:

• List of identified resources based on: CollaborationProject.1.0.0.md and CollaborationProject.1.0.0.json