v0.3.0: Add basic auth (#54)

* Add basic auth for submission.

This commit adds the help text to allow omitting the password, but that
is TODO due to the added complexity and dependencies.

* Add prompting for missing password arg.

* Add testing of basic auth.

* Cast password to string for opts use.

* Fix Opts struct names.

* Add README info about basic auth flags.

* Remove redundant test handler func.

* fix indentation of authuser and authpass

Co-authored-by: Derek <derektamsen@users.noreply.github.com>