[APIT-2476] Terraform provider does not work well when deploying a Flink Model/Statement that uses sql.secrets.*

[tmalikconfluent]

Release Notes

New Features

• [Briefly describe new features introduced in this PR].

Bug Fixes

• Support sensitive properties for Flink statements.

Examples

• [Briefly describe any Terraform configuration example updates in this PR].

Checklist

• I can successfully build and use a custom Terraform provider binary for Confluent.
• I have verified my PR with real Confluent Cloud resources in a pre-prod or production environment, or both.
• I have attached manual Terraform verification results or screenshots in the Test & Review section below.
• I have included appropriate Terraform acceptance or unit tests for any new resource, data source, or functionality.
• I confirm that this PR introduces no breaking changes or backward compatibility issues.
• I have updated the corresponding documentation and include relevant examples for this PR.
• I have indicated the potential customer impact if something goes wrong in the Blast Radius section below.
• I have put checkmarks below confirming that the feature associated with this PR is enabled in:
  • Confluent Cloud prod
  • Confluent Cloud stag
  • Check this box if the feature is enabled for certain organizations only

What

Support sensitive properties for Flink statements.

Blast Radius

All customers using flink statement, specially sensitive properties

References

#397

Test & Review

Added integration tests.
Manual testing Doc: https://docs.google.com/document/d/1RCqKlMJ7Oy_h5dyeeNHKy4iN2nRSNu_22I504xpKGMg/edit?tab=t.0