azurerm_mysql_flexible_server: 8.4 version support

[gerrytan]

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Description

Adds support for version 8.4 and 9.3.

9.3 is an innovation release that has only 30 day lifecycle, but it is supported regardless for 2 reasons:
1. It will be stable in the future
2. Customers can evaluate via Terraform in their testing environment

Update 2025-11-19: 9.3 version support has been dropped from this PR. See discussion.

The version enum is not available in the current API spec 2023-12-30, and not even in latest stable 2024-12-30, so I have to resort to add separate constants. A bug has been filed for this: Azure/azure-rest-api-specs#38382.

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Changes to existing Resource / Data Source

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Testing

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https://hashicorp.teamcity.com/buildConfiguration/TF_AzureRM_AZURERM_SERVICE_PUBLIC_MYSQL/532834

The 4 test failures are pre-existing from main: https://hashicorp.teamcity.com/buildConfiguration/TF_AzureRM_AZURERM_SERVICE_PUBLIC_MYSQL/526380

Change Log

Below please provide what should go into the changelog (if anything) conforming to the Changelog Format documented here.

• azurerm_mysql_flexible_server: 8.4 and 9.3 version support

This is a (please select all that apply):

• Bug Fix
• New Feature (ie adding a service, resource, or data source)
• Enhancement
• Breaking Change

Related Issue(s)

Closes #30677

AI Assistance Disclosure

• AI Assisted - This contribution was made by, or with the assistance of, AI/LLMs

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the provider.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

Note

If this PR changes meaningfully during the course of review please update the title and description as required.

[sreallymatt]

Thanks @gerrytan, I've left a couple comments inline

[sreallymatt]

9.3 is not GA, we generally don't add preview features to the azurerm provider except in exceptional circumstances.

[gerrytan]

@sreallymatt see the reasons I put on the PR description. The API itself is stable, and I've already added a note in the doc about this.

Including this would benefit customers that want to evaluate 9.3 in their testing environment using azurerm Terraform.

[sreallymatt]

The API itself may be stable but the functionality isn't as it's still documented as being in a preview state rather than GA?

[gerrytan]

Ok I'll remove 9.3 support.

[gerrytan]

Thank you for reviewing @sreallymatt , can you please take a look at this PR again.

[gerrytan]

@sreallymatt 9.3 version support has been dropped, missing enum spec issue comment has been added and I have triggered another acctest run. Please have another look at this PR 🙏.

[sreallymatt]

LGTM ✅

[mbfrahry]

LGTM

[gerrytan]

Thank you @sreallymatt @mbfrahry 🙏

[github-actions]

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