feat: Wiki の管理方法変更（#188） (#195)

Merge branch 'feature/188' of https://git.miteruzo.com/miteruzo/btrc-hub into feature/188

#188

Merge branch 'main' into feature/188

#188

#188

#188

#188

Co-authored-by: miteruzo <miteruzo@naver.com>
Reviewed-on: #195

backend/app/models/wiki_revision_line.rb

@@ -0,0 +1,8 @@
+class WikiRevisionLine < ApplicationRecord
+  belongs_to :wiki_revision
+  belongs_to :wiki_line
+
+  validates :position, presence: true,
+                       numericality: { only_integer: true, greater_than_or_equal_to: 0 }
+  validates :position, uniqueness: { scope: :wiki_revision_id }
+end