Only use credentials which have registry configured

[JamieMagee]

We're seeing exceptions like this:

ERROR <job_f1193657-1f45-4e15-a1c9-f51909c517e2> Error processing @babel/traverse (NoMethodError)
ERROR <job_f1193657-1f45-4e15-a1c9-f51909c517e2> undefined method `gsub' for nil:NilClass
 
               url = "#{details['registry'].gsub(%r{/+$}, '')}/#{escaped_dependency_name}"
                                           ^^^^^
ERROR <job_f1193657-1f45-4e15-a1c9-f51909c517e2> /home/dependabot/npm_and_yarn/lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:78:in `block in first_registry_with_dependency_details'

This should prevent us selecting credentials which are missing the registry key.

[abdulapopoola]

please can we get a test for this?

[JamieMagee]

Will add a test.

CI failures are due to rate limits.

[JamieMagee]

The unit test fails on main with the following error

dependabot-core/npm_and_yarn on  main [$!]
❯ bundle exec rspec spec/dependabot/npm_and_yarn/update_checker/registry_finder_spec.rb

Randomized with seed 56745
.................F............................

Failures:

  1) Dependabot::NpmAndYarn::UpdateChecker::RegistryFinder registry with credentials that don't have a registry
     Failure/Error: url = "#{details['registry'].gsub(%r{/+$}, '')}/#{escaped_dependency_name}"

     NoMethodError:
       undefined method `gsub' for nil:NilClass

                     url = "#{details['registry'].gsub(%r{/+$}, '')}/#{escaped_dependency_name}"
                                                 ^^^^^
     # ./lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:78:in `block in first_registry_with_dependency_details'
     # ./lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:77:in `each'
     # ./lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:77:in `find'
     # ./lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:77:in `first_registry_with_dependency_details'
     # ./lib/dependabot/npm_and_yarn/update_checker/registry_finder.rb:34:in `registry'
     # ./spec/dependabot/npm_and_yarn/update_checker/registry_finder_spec.rb:160:in `block (3 levels) in <top (required)>'
     # ./spec/dependabot/npm_and_yarn/update_checker/registry_finder_spec.rb:414:in `block (4 levels) in <top (required)>'
     # /home/jamie/src/work/dependabot-core/common/spec/spec_helper.rb:47:in `block (2 levels) in <top (required)>'

Finished in 0.04251 seconds (files took 0.77595 seconds to load)
46 examples, 1 failure

Failed examples:

rspec ./spec/dependabot/npm_and_yarn/update_checker/registry_finder_spec.rb:414 # Dependabot::NpmAndYarn::UpdateChecker::RegistryFinder registry wi
th credentials that don't have a registry

Same as we see in production.