Use Pull Request number instead of ID

Also avoid using long running transaction
in ExternalPullRequest::CreatePipelineService

ee/app/services/process_github_pull_request_event_service.rb

@@ -20,8 +20,11 @@ class ProcessGithubPullRequestEventService < ::BaseService
     # and the pipeline is created for all newly pushed branches.
     # At that point we will be able to reference it back if a pull request
     # was created.
-    ExternalPullRequest.create_or_update_from_params(params) do |pr|
-      ExternalPullRequests::CreatePipelineService.new(project, current_user).execute(pr)
+    ExternalPullRequest.create_or_update_from_params(params).tap do |pull_request|
+      if pull_request.errors.empty?
+        ExternalPullRequests::CreatePipelineService.new(project, current_user)
+          .execute(pull_request)
+      end
     end
   end
 
@@ -30,7 +33,7 @@ class ProcessGithubPullRequestEventService < ::BaseService
   def params_from_webhook(params)
     {
       project_id: project.id,
-      pull_request_iid: params.dig(:pull_request, :id),
+      pull_request_iid: params.dig(:pull_request, :number),
       source_branch: params.dig(:pull_request, :head, :ref),
       source_sha: params.dig(:pull_request, :head, :sha),
       source_repository: params.dig(:pull_request, :head, :repo, :full_name),

ee/changelogs/unreleased/fix-external-pull-request-id.yml

+---
+title: Use Pull Request number instead of internal Pull Request ID
+merge_request: 16504
+author:
+type: fixed

ee/lib/api/project_mirror.rb

@@ -48,7 +48,7 @@ module API
 
       # pull_request params
       optional :action, type: String, desc: 'Pull Request action'
-      optional 'pull_request.id', type: Integer, desc: 'Pull request ID'
+      optional 'pull_request.number', type: Integer, desc: 'Pull request IID'
       optional 'pull_request.head.ref', type: String, desc: 'Source branch'
       optional 'pull_request.head.sha', type: String, desc: 'Source sha'
       optional 'pull_request.head.repo.full_name', type: String, desc: 'Source repository'

ee/spec/requests/api/project_mirror_spec.rb

@@ -94,7 +94,7 @@ describe API::ProjectMirror do
         let(:params) do
           {
             pull_request: {
-              id: 123,
+              number: 123,
               head: {
                 ref: source_branch,
                 sha: source_sha,

ee/spec/services/process_github_pull_request_event_service_spec.rb

@@ -9,7 +9,7 @@ describe ProcessGithubPullRequestEventService do
   let(:params) do
     {
       pull_request: {
-        id: 123,
+        number: 123,
         head: {
           ref: source_branch,
           sha: source_sha,