Rework migrations for MySQL

migrations/2018-05-25-232323_update_attachments_reference/up.sql

@@ -1,8 +1,8 @@
 ALTER TABLE attachments RENAME TO oldAttachments;
 
 CREATE TABLE attachments (
-  id          TEXT    NOT NULL PRIMARY KEY,
-  cipher_uuid TEXT    NOT NULL REFERENCES ciphers (uuid),
+  id          VARCHAR(40) NOT NULL PRIMARY KEY,
+  cipher_uuid VARCHAR(40) NOT NULL REFERENCES ciphers (uuid),
   file_name   TEXT    NOT NULL,
   file_size   INTEGER NOT NULL
 
@@ -11,4 +11,4 @@ CREATE TABLE attachments (
 INSERT INTO attachments (id, cipher_uuid, file_name, file_size) 
 SELECT id, cipher_uuid, file_name, file_size FROM oldAttachments;
 
-DROP TABLE oldAttachments;
+DROP TABLE oldAttachments;