[VI-1012] adds SiS pkey jwt ClientConfig seed

[bramleyjl]

Summary

• This work is behind a feature toggle (flipper): NO
• Updates development seed file to include an example SignIn::ClientConfig for private key JWT clients

Related issue(s)

• Companion PR to a larger Identity Postman update.
• https://jira.devops.va.gov/browse/VI-1012

Testing done

• New code is covered by unit tests

Token request testing

• pull down the latest Postman collection update
• run the seed file: bin/rails db:seed
• verify the new ClientConfig exists

SignIn::ClientConfig.find_by(client_id: 'sample_client_pkey_jwt').client_id
=> "sample_client_pkey_jwt"

• call the SiS /authorize endpoint with the sample_client_pkey_jwt client id & authenticate

http://localhost:3000/v0/sign_in/authorize?type=idme&acr=loa3&client_id=sample_client_pkey_jwt&code_challenge=JNkFflCkxk1K6gQUf23P_5Ctl_T65_xkkOU_y-Cc2XI=&code_challenge_method=S256&state=c4addf6001661631d2524043ca31107e

• copy the returned code URL parameter into the Postman collection as the sis_client-auth_code variable & make a Sign In Service / Client Auth (User) / Private Key JWT Auth / token request - you should receive a 200 response with access & refresh tokens
  

Token usage testing

• update vets-api/app/controllers/concerns/authentication_and_sso_concerns.rb to allow the sample_client_pkey_jwt client id to access authenticated routes

  included do
    before_action :authenticate, :set_session_expiration_header

    validates_access_token_audience ['sample_client_pkey_jwt', Settings.sign_in.vaweb_client_id, ('vamock' if MockedAuthentication.mockable_env?)]
  end

• Make a Postman request to an authenticated route, such as the vets-api / User / ICN call - you should receive a 200 response