feat: mark skipped checks as skipped (#12606)

A separate commit status is introduced for skipped checks. That enables marking them as such in the UI instead of successful, which could be misleading.

Resolves https://codeberg.org/forgejo/forgejo/issues/10138.

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. All work and communication must conform to Forgejo's [AI Agreement](https://codeberg.org/forgejo/governance/src/branch/main/AIAgreement.md). There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests for Go changes

(can be removed for JavaScript changes)

- I added test coverage for Go changes...
  - [x] in their respective `*_test.go` for unit tests.
  - [x] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
  - [x] `make pr-go` before pushing

### Tests for JavaScript changes

(can be removed for Go changes)

- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.

*The decision if the pull request will be shown in the release notes is up to the mergers / release team.*

The content of the `release-notes/<pull request number>.md` file will serve as the basis for the release notes. If the file does not exist, the title of the pull request will be used instead.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12606
Reviewed-by: Cyborus <cyborus@disroot.org>
Reviewed-by: Mathieu Fenniak <mfenniak@noreply.codeberg.org>

models/fixtures/commit_status.yml

@@ -93,3 +93,15 @@
   context: deploy/awesomeness
   context_hash: ae9547713a6665fc4261d0756904932085a41cf2
   creator_id: 2
+
+-
+  id: 9
+  index: 7
+  repo_id: 1
+  state: "skipped"
+  sha: "1234123412341234123412341234123412341234"
+  target_url: https://example.com/builds/
+  description: Publish awesomeness
+  context: publish/awesomeness
+  context_hash: 701785a796917a4942f2ab1337d95225270026b5
+  creator_id: 2

models/git/commit_status_test.go

@@ -33,8 +33,8 @@ func TestGetCommitStatuses(t *testing.T) {
 		SHA:         sha1,
 	})
 	require.NoError(t, err)
-	assert.EqualValues(t, 6, maxResults)
-	assert.Len(t, statuses, 6)
+	assert.EqualValues(t, 7, maxResults)
+	assert.Len(t, statuses, 7)
 
 	assert.Equal(t, "ci/awesomeness", statuses[0].Context)
 	assert.Equal(t, structs.CommitStatusPending, statuses[0].State)
@@ -60,13 +60,17 @@ func TestGetCommitStatuses(t *testing.T) {
 	assert.Equal(t, structs.CommitStatusPending, statuses[5].State)
 	assert.Equal(t, "https://try.gitea.io/api/v1/repos/user2/repo1/statuses/1234123412341234123412341234123412341234", statuses[5].APIURL(db.DefaultContext))
 
+	assert.Equal(t, "publish/awesomeness", statuses[6].Context)
+	assert.Equal(t, structs.CommitStatusSkipped, statuses[6].State)
+	assert.Equal(t, "https://try.gitea.io/api/v1/repos/user2/repo1/statuses/1234123412341234123412341234123412341234", statuses[6].APIURL(db.DefaultContext))
+
 	statuses, maxResults, err = db.FindAndCount[git_model.CommitStatus](db.DefaultContext, &git_model.CommitStatusOptions{
 		ListOptions: db.ListOptions{Page: 2, PageSize: 50},
 		RepoID:      repo1.ID,
 		SHA:         sha1,
 	})
 	require.NoError(t, err)
-	assert.EqualValues(t, 6, maxResults)
+	assert.EqualValues(t, 7, maxResults)
 	assert.Empty(t, statuses)
 }
 
@@ -182,6 +186,29 @@ func Test_CalcCommitStatus(t *testing.T) {
 				State: structs.CommitStatusError,
 			},
 		},
+		{
+			statuses: []*git_model.CommitStatus{
+				{
+					State: structs.CommitStatusSkipped,
+				},
+			},
+			expected: &git_model.CommitStatus{
+				State: structs.CommitStatusSkipped,
+			},
+		},
+		{
+			statuses: []*git_model.CommitStatus{
+				{
+					State: structs.CommitStatusSuccess,
+				},
+				{
+					State: structs.CommitStatusSkipped,
+				},
+			},
+			expected: &git_model.CommitStatus{
+				State: structs.CommitStatusSuccess,
+			},
+		},
 		{
 			statuses: []*git_model.CommitStatus{},
 			expected: nil,