Don't allow same foreign keys

packages/builder/src/components/backend/Datasources/CreateEditRelationship.svelte

@@ -195,7 +195,8 @@
           throughTable,
           fromTable.primary[0],
           throughToKey
-        ),
+        ) ||
+        errorChecker.differentColumns(throughFromKey, throughToKey),
       throughToKey:
         errorChecker.manyForeignKeySet(throughToKey) ||
         errorChecker.manyTypeMismatch(

packages/builder/src/components/backend/Datasources/relationshipErrors.js

@@ -3,6 +3,7 @@ import { RelationshipType } from "@budibase/types"
 const typeMismatch = "Column type of the foreign key must match the primary key"
 const columnBeingUsed = "Column name cannot be an existing column"
 const mustBeDifferentTables = "From/to/through tables must be different"
+const mustBeDifferentColumns = "Foreign keys must be different"
 const primaryKeyNotSet = "Please pick the primary key"
 const throughNotNullable =
   "Ensure non-key columns are nullable or auto-generated"
@@ -83,6 +84,11 @@ export class RelationshipErrorChecker {
     return error ? mustBeDifferentTables : null
   }
 
+  differentColumns(columnA, columnB) {
+    const error = columnA && columnB && columnA === columnB
+    return error ? mustBeDifferentColumns : null
+  }
+
   columnBeingUsed(table, column, ogName) {
     return isColumnNameBeingUsed(table, column, ogName) ? columnBeingUsed : null
   }