Allow using Action Mailbox on MySQL 5.5

Active Record still support MySQL 5.5 which doesn't support datetime
with precision.

https://github.com/rails/rails/blob/9e34df00039d63b5672315419e76f06f80ef3dc4/activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb#L99-L101

So we should check `supports_datetime_with_precision?` on the
connection.

1 files changed, 17 insertions, 0 deletions

diff --git a/actionmailbox/test/dummy/db/migrate/20180208205311_create_action_mailbox_tables.rb b/actionmailbox/test/dummy/db/migrate/20180208205311_create_action_mailbox_tables.rb
new file mode 100644
index 0000000000..89ab66c1a9
--- /dev/null
+++ b/actionmailbox/test/dummy/db/migrate/20180208205311_create_action_mailbox_tables.rb
@@ -0,0 +1,17 @@
+class CreateActionMailboxTables < ActiveRecord::Migration[6.0]
+  def change
+    create_table :action_mailbox_inbound_emails do |t|
+      t.integer :status, default: 0, null: false
+      t.string  :message_id, null: false
+      t.string  :message_checksum, null: false
+
+      if supports_datetime_with_precision?
+        t.timestamps precision: 6
+      else
+        t.timestamps
+      end
+
+      t.index [ :message_id, :message_checksum ], name: "index_action_mailbox_inbound_emails_uniqueness", unique: true
+    end
+  end
+end