fix: Set the default branch if it's not already set on Github integration (#44332)

Previously, the POST to `/v1/projects/{ref}/branches` didn't work on
free projects, which left some Supabase projects setup without a default
branch. Easy fix for those projects would be to disable/enable the whole
integration.

This PR fixes that so that when the user wants to setup a production
sync, the code checks if there's branches already setup and if not, sets
the selected branch as default.

---------

Co-authored-by: Joshen Lim <joshenlimek@gmail.com>

apps/studio/components/interfaces/Settings/Integrations/GithubIntegration/GitHubIntegrationConnectionForm.tsx

@@ -323,6 +323,14 @@ export const GitHubIntegrationConnectionForm = ({
         gitBranch: data.enableProductionSync ? data.branchName : '',
         branchName: data.branchName || 'main',
       })
+    } else {
+      // if for some reason, the project doesn't have a default branch yet, create it.
+      createBranch({
+        projectRef: selectedProject.ref,
+        gitBranch: data.enableProductionSync ? data.branchName : '',
+        branchName: data.branchName || 'main',
+        is_default: true,
+      })
     }
 
     setIsConfirmingBranchChange(false)
@@ -771,7 +779,7 @@ export const GitHubIntegrationConnectionForm = ({
                         </Button>
                       )}
                       <Button
-                        type="default"
+                        type="primary"
                         htmlType="submit"
                         disabled={
                           !hasAccessToGitHubIntegration ||