aliases/implications: log manual deletions by admins.

Log when an admin manually deletes an alias or implication outside of a
BUR. This is usually only necessary when a BUR is bugged.

app/models/mod_action.rb

@@ -46,8 +46,10 @@ class ModAction < ApplicationRecord
     forum_post_delete: 102,
     tag_alias_create: 120,
     tag_alias_update: 121, # XXX unused
+    tag_alias_delete: 122,
     tag_implication_create: 140,
     tag_implication_update: 141, # XXX unused
+    tag_implication_delete: 142,
     ip_ban_create: 160,
     ip_ban_delete: 162,
     ip_ban_undelete: 163,

app/models/tag_alias.rb

@@ -43,6 +43,6 @@ class TagAlias < TagRelationship
     tag_relationships << TagAlias.active.find_by(antecedent_name: consequent_name, consequent_name: antecedent_name)
     tag_relationships << TagImplication.active.find_by(antecedent_name: antecedent_name, consequent_name: consequent_name)
     tag_relationships << TagImplication.active.find_by(antecedent_name: consequent_name, consequent_name: antecedent_name)
-    tag_relationships.each { |rel| rel.reject! if rel.present? }
+    tag_relationships.each { |rel| rel.reject!(User.system) if rel.present? }
   end
 end

app/models/tag_relationship.rb

@@ -43,8 +43,16 @@ class TagRelationship < ApplicationRecord
     status == "active"
   end
 
-  def reject!
+  # Mark an alias or implication as deleted, and log a mod action if the
+  # deletion was manually performed by an admin, as opposed to automatically by
+  # DanbooruBot as part of a BUR.
+  def reject!(rejector = CurrentUser.user)
     update!(status: "deleted")
+
+    if rejector != User.system
+      category = relationship == "tag alias" ? :tag_alias_delete : :tag_implication_delete
+      ModAction.log("deleted #{relationship} #{antecedent_name} -> #{consequent_name}", category, rejector)
+    end
   end
 
   module SearchMethods