Create specs to test compatibility with the license names returned by Gitaly

Gitaly detects the license of a repository and gitlab processes that output to show the license information.

During the roll-out of gitaly!3797 (merged) there was an incident raised.

The reason: the Licensee gem database does not match the license database used by go-license-detector. To prevent us from running into a similar problem again, we should test compatibility:

• test for each of the licenses supported by Licensee if Gitaly returns them correctly.
• test if GitLab gracefully ignores licenses not supported by Licensee.