feat: add keys attribute to okta_app_saml resource

[ericnorris]

This pull request adds a keys attribute to the okta_app_saml resource. We've put the methods used to pull the data into app.go, so it could potentially be added to other okta_app_* resources, and also their matching data sources.

Our use case is in setting up org2org with OAuth, where we'd like to create an okta_app_saml resource in one organization, and an okta_app_oauth service app in the other.

Without the keys attribute, we've resorted to manually calling the /credentials/keys endpoint and adding them as JWK blocks in okta_app_oauth. We'd prefer to have this process be as automated as possible, so adding the keys to the application resource made sense to us.

[monde]

Thanks for the PR @ericnorris ! Apologies for the slow reply as I'm just getting back from vacation. I should be able to look at this by the end of this week.

[ericnorris]

Hey @monde, apologies for the ping, but any chance you'd be able to take a look at this PR this week or next?

[monde]

got test confirmation from @ericnorris and @slichtenthal

=== RUN   TestAccAppSaml_conditionalRequire
--- PASS: TestAccAppSaml_conditionalRequire (5.35s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	5.647s
=== RUN   TestAccAppSaml_invalidURL
--- PASS: TestAccAppSaml_invalidURL (1.79s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	2.107s
=== RUN   TestAccAppSaml_crud
--- PASS: TestAccAppSaml_crud (55.85s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	56.183s
=== RUN   TestAccAppSaml_preconfigured
--- PASS: TestAccAppSaml_preconfigured (47.41s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	48.140s
=== RUN   TestAccAppSaml_userGroups
--- PASS: TestAccAppSaml_userGroups (33.04s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	33.404s
=== RUN   TestAccAppSaml_inlineHook
--- PASS: TestAccAppSaml_inlineHook (45.70s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	46.090s
=== RUN   TestAccAppSaml_federationBroker
    resource_okta_app_saml_test.go:302: This is an 'Early Access Feature' and needs to be enabled by Okta, skipping this test as it fails when this feature is not available
--- SKIP: TestAccAppSaml_federationBroker (0.00s)
PASS
ok  	github.com/okta/terraform-provider-okta/okta	0.407s

[monde]

good to go @ericnorris and @slichtenthal

[monde]

Released in https://github.com/okta/terraform-provider-okta/releases/tag/v3.32.0