Fixed migration util dropping foreign keys before columns

- if we add a column with a foreign key reference, the `down` migration
  will try to remove that column
- you can't remove a column without deleting the foreign key reference
  first
- our migration utils didn't take that into account and there's nothing
  in Knex to do this for us
- this commit deletes the foreign key before removing the column if we
  have one referenced in the column spec
- also updates the code to pass the column spec into the util

core/server/data/migrations/utils.js

@@ -375,7 +375,8 @@ function createAddColumnMigration(table, column, columnDefinition) {
             column,
             dbIsInCorrectState: hasColumn => hasColumn === false,
             operation: commands.dropColumn,
-            operationVerb: 'Removing'
+            operationVerb: 'Removing',
+            columnDefinition
         })
     );
 }

core/server/data/schema/commands.js

@@ -65,7 +65,12 @@ function addColumn(tableName, column, transaction = db.knex, columnSpec) {
     });
 }
 
-function dropColumn(tableName, column, transaction = db.knex) {
+async function dropColumn(tableName, column, transaction = db.knex, columnSpec = {}) {
+    if (Object.prototype.hasOwnProperty.call(columnSpec, 'references')) {
+        const [toTable, toColumn] = columnSpec.references.split('.');
+        await dropForeign({fromTable: tableName, fromColumn: column, toTable, toColumn, transaction});
+    }
+
     return transaction.schema.table(tableName, function (table) {
         table.dropColumn(column);
     });