Add visible projects API

What does this MR do?

Add a new /projects/visible API endpoint. Originally created by @ben.boeckel in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5970.

Are there points in the code the reviewer needs to double check?

Does the API make sense?

Why was this MR needed?

The /projects endpoint only returned projects the user was explicitly a member of.

What are the relevant issue numbers?

Closes #19361 (closed), #3119 (closed).

Screenshots (if relevant)

N/A

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

Changed title: Ben.boeckel/gitlab ce api visible projects → Add visible projects API

Mentioned in merge request !5970 (closed)

/cc @tiagonbotelho for the doc changes!

@smcgivern I left just a few comments.

Reassigned to @smcgivern

@smcgivern yep that about sums it up :) thank you!

@grzesiek thanks! Can you take another look please?

Reassigned to @grzesiek

Added 1 commit:

• 0a1baaa8 - Tidy up project list actions

@smcgivern LGTM 👍 Thanks!

Reassigned to @rymai

Reassigned to @smcgivern

Added 1 commit:

• 7623ab0c - Make projects API docs match parameter style

Reassigned to @rymai

Resolved all discussions

Mentioned in merge request !6706 (closed)

Thanks @smcgivern! LGTM! ❤️ And thanks for improving the doc!!

Status changed to merged

Mentioned in commit 1be15162

Resolved all discussions

Mentioned in issue #23555 (closed)

Mentioned in merge request !7007 (merged)

Mentioned in commit ba28a64e

Mentioned in merge request gitlab-com/www-gitlab-com!3412 (merged)

Mentioned in commit 0e1a9482