[FEAT] Configure if protected branch rule should apply to admins

- Currently protected branch rules do not apply to admins, however in
some cases (like in the case of Forgejo project) you might also want to
apply these rules to admins to avoid accidental merges.
- Add new option to configure this on a per-rule basis.
- Adds integration tests.
- Resolves #65

routers/private/hook_pre_receive.go

@@ -337,13 +337,9 @@ func preReceiveBranch(ctx *preReceiveContext, oldCommitID, newCommitID string, r
 			return
 		}
 
-		// If we're an admin for the repository we can ignore status checks, reviews and override protected files
-		if ctx.userPerm.IsAdmin() {
-			return
-		}
-
-		// Now if we're not an admin - we can't overwrite protected files so fail now
-		if changedProtectedfiles {
+		// It's not allowed t overwrite protected files. Unless if the user is an
+		// admin and the protected branch rule doesn't apply to admins.
+		if changedProtectedfiles && (!ctx.user.IsAdmin || protectBranch.ApplyToAdmins) {
 			log.Warn("Forbidden: Branch: %s in %-v is protected from changing file %s", branchName, repo, protectedFilePath)
 			ctx.JSON(http.StatusForbidden, private.Response{
 				UserMsg: fmt.Sprintf("branch %s is protected from changing file %s", branchName, protectedFilePath),
@@ -352,8 +348,12 @@ func preReceiveBranch(ctx *preReceiveContext, oldCommitID, newCommitID string, r
 		}
 
 		// Check all status checks and reviews are ok
-		if err := pull_service.CheckPullBranchProtections(ctx, pr, true); err != nil {
+		if pb, err := pull_service.CheckPullBranchProtections(ctx, pr, true); err != nil {
 			if models.IsErrDisallowedToMerge(err) {
+				// Allow this if the rule doesn't apply to admins and the user is an admin.
+				if ctx.user.IsAdmin && !pb.ApplyToAdmins {
+					return
+				}
 				log.Warn("Forbidden: User %d is not allowed push to protected branch %s in %-v and pr #%d is not ready to be merged: %s", ctx.opts.UserID, branchName, repo, pr.Index, err.Error())
 				ctx.JSON(http.StatusForbidden, private.Response{
 					UserMsg: fmt.Sprintf("Not allowed to push to protected branch %s and pr #%d is not ready to be merged: %s", branchName, ctx.opts.PullRequestID, err.Error()),