SSO: Convert numeric durations to strings in SSO settings

[dmihai]

When importing SAML settings into Terraform, it is possible that some duration fields coming from the API to have a numeric type. This will generate an error because their type in Terraform is string:

[ERROR] setting state: saml_settings.0.max_issue_delay: '' expected type 'string', got unconvertible type 'float64', value: '3e+11'

This fix will convert all numeric durations from the settings map to strings.

[github-actions]

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To do so, a Grafana Labs employee must trigger the cloud acceptance tests workflow manually.

[mgyongyosi]

Thanks, it works like a charm! Tested locally and the max_issue_delay and metadata_valid_duration are handled correctly. 🎉