Add an invoice payment method

The site sells services and tickets for events. Now only card payment is available.
It is necessary to create an invoice for payment, duplicate it to the users email, pull it up in the Quality Control Personal Account.

Need:
1. Conduct a code review
2. Make a TK for work.
3. Perform work on the TK.

Project on Yii2.
Detailed on the project of our TK on the part of the client will be provided after signing the NDA.
Interested in long-term cooperation under an agreement with an individual entrepreneur or a self-employed specialist.
Please send examples of your projects and code right away.