Add transactions support

[xiaoyi510]

MongoDB 4.x 已经支持事务,但是yii2扩展mongodb暂不支持事务操作

MongoDB 4.x already supports transactions, but yii2 extended mongodb does not support transaction operations temporarily

[samdark]

There are two pull requests:

• Transactions support #294
• Transaction support #276

In order to properly check it we need to switch to GitHub actions and fix tests: #279

[alxark]

any plans to implement transactions?

[bizley]

Would you like to help with the implementation?

[alxark]

Would you like to help with the implementation?

what about this PR #276 ? at least to start from.

[bizley]

Yes, you can continue from there. We switched to Github actions so it should be easier, the PR requires tests though.