Add validation and error summary to comment form

[Abban]

• Pull axios out of the DonationCommentPopUp component and wraps it in a resource.
• Add tests for post response handling
• Add check for empty comment on submit
• Add new error for when the comment is empty
• Add error type var to display the correct error
• Add tests

Ticket: https://phabricator.wikimedia.org/T367387

[Abban]

We need to wait until #464 is merged to get rid of the build error

[gbirke]

I like the new code, the new approach for pulling out server communication as a service improves quality and the error display works well. However, I user-tested the frontend code with the current PHP code and it does not work, because axios.post by default sends a JSON body instead of the form-encoded fields that our current endpoint expects.

You can now either use a FormData object and the correct Axios headers to send the data (see other services in src/api) or we could take the opportunity to add an API endpoint to the fundraising app that accepts JSON. I've created a suggestion in wmde/fundraising-application#2992 which you can adapt as you see fit.

[Abban]

Lol, did I manage to only acceptance test the unhappy paths?

[gbirke]

Works now