Add contributor pub membership when user creates pub

[gabestein]

Motivation

So contributors who create new pubs (via public form, related fields, or internal create form) can edit them later using the form they used to create it

Requirements

• When a user creates a new pub, they are automatically given a contributor membership to it, with a form permission for the form they used to fill it out.

Acceptance Criteria

• Should create new membership for the user/pub, with formid of form used to create pub

[gabestein]

@kalilsn and/or @tefkah -- per your slack comment, I think we basically decided to do this in #1002/#1051. Is that right?

[kalilsn]

I think so, specifically a contributor pub membership with the id of the form they submitted. And then #1098 will make that just one of several options