#280 Stripe BillingInfo front-end form and validation (fe + be)

[amihaiemil]

Fixes #280

Added the front-end form and validation;
Added backend param bean and validation;
Saving BillingInfo to Stripe Customer (wallet).

[charlesmike]

@amihaiemil thank you for your Pull Request. I'll assign someone to review it soon.

[charlesmike]

@amihaiemil please review this Pull Request. Deadline (when it should be merged or closed) is 2020-12-22T18:04:55.133704.

You should check if the requirements have been implemented (partially or in full), if there are unit tests covering the changes and if the CI build passes. Feel free to reject the PR or ask for changes if it's too big or not clear enough.

Estimation here is 30 minutes, that's how much you will be paid. You will be paid even if this PR gets rejected.

[charlesmike]

@amihaiemil Don't forget to close this ticket before the deadline (2020-12-22T18:04:55). You are past the first half of the allowed period.

[charlesmike]

@amihaiemil thank you for resolving this ticket. I've just added it to your active invoice. You can always check all your invoices and more on the Contributor Dashboard.