fix: make migrate down work on migrations

Ensure that irreversible migrations are marked as such, that type
conversions are implemented correctly, and that the changes are executed
in the right order.

Author: ethanwu10

migrations/1581725957097_del-password.js

@@ -2,8 +2,4 @@ exports.up = function (pgm) {
   pgm.dropColumns('users', ['password'])
 }
 
-exports.down = function (pgm) {
-  pgm.addColumns('users', {
-    password: { type: 'string', notNull: true }
-  })
-}
+exports.down = false

migrations/1582424634372_string-uuids.js

@@ -5,7 +5,7 @@ exports.up = function (pgm) {
 }
 
 exports.down = function (pgm) {
-  pgm.alterColumn('users', 'id', { type: 'uuid' })
-  pgm.alterColumn('solves', 'id', { type: 'uuid' })
-  pgm.alterColumn('solves', 'userid', { type: 'uuid' })
+  pgm.alterColumn('users', 'id', { type: 'uuid', using: 'id::uuid' })
+  pgm.alterColumn('solves', 'id', { type: 'uuid', using: 'id::uuid' })
+  pgm.alterColumn('solves', 'userid', { type: 'uuid', using: 'id::uuid' })
 }

migrations/1585799727940_add-ctftime-id.js

@@ -7,7 +7,7 @@ exports.up = function (pgm) {
 }
 
 exports.down = function (pgm) {
-  pgm.dropColumns('users', ['ctftime_id'])
-  pgm.alterColumn('users', 'email', { notNull: true })
   pgm.dropConstraint('users', 'require_email_or_ctftime_id')
+  pgm.alterColumn('users', 'email', { notNull: true })
+  pgm.dropColumns('users', ['ctftime_id'])
 }