POST and GET for /to/<username> should be hosted on the same endpoint to allow for form resubmits

[brassy-endomorph]

Is your feature request related to a problem? Please describe.

When a user submits a form, if the GET and POST are in the same endpoint, failed input can be recycled when the page is re-rendered so that they don't have to type things again. Currently this endpoint stores the answer to the captcha in the session, so if multiple tabs are open, only one will correctly submit.

Describe the solution you'd like

Merge the two endpoints and use if/else on the request.method