Remove unused foreign key model

src/metabase/api/table.clj

@@ -77,7 +77,7 @@
                                                   (not= (keyword visibility_type) :sensitive)))))))
 
 (defendpoint GET "/:id/fks"
-  "Get all `ForeignKeys` whose destination is a `Field` that belongs to this `Table`."
+  "Get all foreign keys whose destination is a `Field` that belongs to this `Table`."
   [id]
   (let-404 [table (Table id)]
     (read-check table)

src/metabase/cmd/load_from_h2.clj

@@ -17,7 +17,6 @@
                              [dependency :refer [Dependency]]
                              [field :refer [Field]]
                              [field-values :refer [FieldValues]]
-                             [foreign-key :refer [ForeignKey]]
                              [label :refer [Label]]
                              [metric :refer [Metric]]
                              [pulse :refer [Pulse]]
@@ -49,7 +48,6 @@
    Table
    Field
    FieldValues
-   ForeignKey
    Segment
    Metric
    Revision

src/metabase/db/migrations.clj

@@ -9,7 +9,6 @@
                              [dashboard-card :refer [DashboardCard]]
                              [database :refer [Database]]
                              [field :refer [Field]]
-                             [foreign-key :refer [ForeignKey]]
                              [interface :refer [defentity]]
                              [raw-column :refer [RawColumn]]
                              [raw-table :refer [RawTable]]
@@ -19,7 +18,10 @@
 
 ;;; # Migration Helpers
 
-(defentity DataMigrations :data_migrations)
+(defentity ^:private DataMigrations :data_migrations)
+
+;; This is defined here since we still need it for some of the data migrations below. It's no longer used.
+(defentity ^:deprecated ^:private ForeignKey :metabase_foreignkey)
 
 (defn- migration-ran? [migration-name]
   (db/exists? DataMigrations :id (name migration-name)))

src/metabase/models/field.clj

@@ -5,7 +5,6 @@
             [metabase.db :as db]
             (metabase.models [common :as common]
                              [field-values :refer [FieldValues]]
-                             [foreign-key :refer [ForeignKey]]
                              [interface :as i])
             [metabase.util :as u]))
 
@@ -88,8 +87,6 @@
 
 (defn- pre-cascade-delete [{:keys [id]}]
   (db/cascade-delete! Field :parent_id id)
-  (db/cascade-delete! ForeignKey {:where [:or [:= :origin_id id]
-                                              [:= :destination_id id]]})
   (db/cascade-delete! 'FieldValues :field_id id))
 
 (defn ^:hydrate target

src/metabase/models/foreign_key.clj

-(ns ^:deprecated metabase.models.foreign-key
-  (:require [metabase.models.interface :as i]
-            [metabase.util :as u]))
-
-;; This namespace is no longer used. We need to keep it around for the time being because some data migrations still refere
-
-(i/defentity ^:deprecated ForeignKey :metabase_foreignkey)
-
-(u/strict-extend (class ForeignKey)
-  i/IEntity
-  (merge i/IEntityDefaults
-         {:types        (constantly {:relationship :keyword})
-          :timestamped? (constantly true)
-          :can-read?    (constantly true)
-          :can-write?   i/superuser?}))