[buddy] Add saml_idp_service_provider resource support to the terraform provider

[tigrato]

Buddy PR for #51586

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Fixes #41874 adding a terraform resource and data source for saml_idp_service_provider

Changelog: Add support for saml_idp_service_provider objects in Terraform module.

[public-teleport-github-review-bot]

@tigrato - this PR will require admin approval to merge due to its size. Consider breaking it up into a series smaller changes.

[github-actions]

Amplify deployment status

Branch	Commit	Job ID	Status	Preview	Updated (UTC)
tigrato/pr-buddy-51586	2df247d	4	✅SUCCEED	tigrato-pr-buddy-51586	2025-02-06 11:18:38

[hugoShaka]

I think @flyinghermit wanted to do a few checks and observe computed fields. Have you got a chance to do them?

[flyinghermit]

Sorry I haven't been able to get to this yet. I will try to get to the review early next week.

The gist is, there are guided and generic SAML service provider configuration. Guided ones are what we call "preset" ones. For both generic and preset types, entity_descriptor is a computed field but we only auto-generate it if its empty. And for the preset types, the relay_state, attribute_mapping and entity_descriptor fields are the computed fields. Since the terraform provider for the saml_idp_service_provider has been of interest for many Teleport users, I just want to ensure what initially works and what does not so the limitations are communicated upfront.

This ticket elaborates more on the issue and is a precursor to support both the generic and preset SAML service provider in terraform #43431.

Edit: Many thanks @dangorst1066 for initiating this PR.