[kbn-test] improve error handling for saml auth

[dmlemeshko]

Summary

If cloud user has no access to the project, we get error message like Error: Failed to parse SAML response value. This error does not explain the issue and especially because request returns 200 OK (due to redirects)

This PR disables redirects for API call that creates SAML response, so if user has no access to the project response code is 303. To better explain the issue extended message is logged:

Error: Failed to parse SAML response value.
 │ Most likely the <user_email> user has no access to the cloud deployment.
 │ Login to <cloud hostname> with the user from '.ftr/role_users.json' file and try to load
 | <project_kibana_url> in the same window.

The PR also adds test coverage for the SAML auth in Cloud, to make sure we don't break stuff with new changes

[dmlemeshko]

/ci

[wayneseymour]

I get the feeling there's a great reason for this, but why 253?

[dmlemeshko]

The entire hostname, including the delimiting dots, has a maximum of 253 ASCII characters

[wayneseymour]

Should this function be typed? Just a tiny almost-a-nit lol

[wayneseymour]

LGTM

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 1840de8

Metrics [docs]

✅ unchanged

History

• 💔 Build #210763 failed ecf1323
• 💔 Build #210189 failed fd31024
• 💛 Build #209788 was flaky a3dfa94
• 💔 Build #209738 failed 5486fc9
• 💚 Build #209408 succeeded d9c3913

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