Attachments - Policy and Service updates for Group and Project attachments

[ChrisHuynh333]

What does this PR do and why?

This policy updates the policies and attachments create service for adding attachments to groups and projects

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other pull requests.

How to set up and validate locally

1. Migrate your database
2. Verify tests pass locally

PR 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 PR acceptance checklist for this PR.

[ericenns]

Looking good, just need a few more tests as specified in the comments. But in addition tests for the attachments destroy service are needed.

[ericenns]

Looks good to me!

[github-actions]

Code Metrics Report

Coverage	Test Execution Time
93.0%	7m18s

Code coverage of files in pull request scope (96.6%)

Files	Coverage
app/models/member.rb	96.8%
app/models/namespace.rb	95.6%
app/policies/group_policy.rb	95.1%
app/policies/project_policy.rb	96.0%
app/services/attachments/create_service.rb	100.0%
app/services/attachments/destroy_service.rb	96.8%
app/views/layouts/projects.html.erb	100.0%

---

Reported by octocov

[deepsidhu85]

Looks good to me!