GitHub integration should default to "Static status check names"

What

Make "Static status check names" the default for our CI integration with GitHub.

Why

Users will often want our integration to be compatible with "Required status checks", so they can prevent pull requests being merged before a pipeline is complete. We introduced a setting to make this possible, but users shouldn't have to find it and might struggle to understand why this needs to be turned on to make things work.

Related

• Mentioned in the description in https://gitlab.com/gitlab-org/gitlab-ee/issues/6696
• Came up in https://gitlab.com/gitlab-org/gitlab-ee/issues/8129#note_144229628
• Might explain some of the demand for having this in the API in https://gitlab.com/gitlab-org/gitlab-ee/issues/8477.