Build user to contributor messaging (P2P)

We want to allow users to make comments or ask questions about a dataset directly to the contributor of that dataset.

[ ] For authenticated users, show a "Contact the Contributor" link next to the Contributor name. Design
- Option: make this visible to unauthenticated users and direct them to the login page. However this is only desired if it is possible to track the dataset the user came from and redirect back to it after log in or account creation.
[ ] The contact link opens a modal for typing the message. Design. The available subjects in the dropdown are: General Inquiry, Comments/Suggestions, Report a Problem with the Data, Other
[ ] below the text entry field, left-justified add this text: "A copy of your message will also be sent to the HDX team." (In my notes about this, we decided not to copy our feedback email, but I can't remember why, so I'm putting it back in)
[ ] in the design, this field is limited to 1000 words. Is that feasible? Limiting the number of characters is also an acceptable plan B.
[ ] Submitting this form sends and email to the dataset maintainer's email address and to our feedback email address. If possible, the reply to for the email should be that of the submitting users (will this get us spam filtered?)
[ ] A standard ckan success/failure message is displayed at the top of the dataset page when the modal is closed.

OCHA-DAP / hdx-ckan