fix: samlidp package resolution

[james-d-elliott]

This fixes the package resolution for samlidp and still allows the tests to complete successfully (or it should). Also performs a go mod tidy.

See https://github.com/golang/go/wiki/Modules#is-it-possible-to-add-a-module-to-a-multi-module-repository

[dcormier]

Fixes #448.

[muir]

I have an alternative fix #475 . I simply get rid of the extra go.mod files

[crewjam]

I think this isn't needed since we dropped the internal go.mod files. Please comment if I'm wrong.

[james-d-elliott]

I am pretty sure that's correct. Nice job @muir.