修复：合并请求评审模型修改

db/migrate/20220725020217_create_pull_requests_reviewers.rb

@@ -0,0 +1,9 @@
+class CreatePullRequestsReviewers < ActiveRecord::Migration[5.2]
+  def change
+    create_table :pull_requests_reviewers do |t|
+      t.belongs_to :pull_request, index: true 
+      t.belongs_to :reviewer, class_name: User, index:true
+      t.timestamps
+    end
+  end
+end

db/migrate/20220725020443_change_reviews_reference_to_pull_requests.rb

@@ -0,0 +1,6 @@
+class ChangeReviewsReferenceToPullRequests < ActiveRecord::Migration[5.2]
+  def change
+    remove_reference :reviews, :issue
+    add_reference :reviews, :pull_request
+  end
+end