Ensure required fields are set before sending form

[rtertiaer]

What does this change intend to accomplish?

This PR checks that every required field for a stream has a value before sending the update to the API. It doesn't do much else in the way of form validation; there's also a case to be made here for actually reading the status of the POST/PATCH for a particular stream, but that's probably a different issue entirely.

This PR fixes #572 .

Checklist

• [x] Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• [x] If applicable, have you updated the documentation/manual?
• [x] If applicable, have you updated the CHANGELOG?
• [x] Does your submission pass linting & tests? You can test on localhost using ./scripts/test

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 51.03%. Comparing base (6653f16) to head (28100b5).

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #650   +/-   ##
=======================================
  Coverage   51.03%   51.03%           
=======================================
  Files          25       25           
  Lines        5774     5774           
=======================================
  Hits         2947     2947           
  Misses       2827     2827           

Flag	Coverage Δ
unittests	51.03% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[rtertiaer]

:sunglasses: