Error when application secret already exists

[jemrobinson]

✅ Checklist

• I have searched open and closed issues for duplicates.
• This is a problem observed when deploying a Data Safe Haven.
• I can reproduce this with the latest version.
• I have read through the documentation.
• This isn't an open-ended question (open a discussion if it is).

💻 System information

• Operating System: macOS
• Data Safe Haven version: develop @ 8e76a2f

🚫 Describe the problem

When trying to deploy an SRE that re-uses an old AzureAD application, a new secret needs to be created with an existing name. This fails with "secret already exists".

We should either

• tear down the AzureAD application when the SRE is torn down
• overwrite the existing secret

🌳 Log messages

Relevant log messages

2024-04-16 11:08:44 [   ERROR]     error: Exception calling application: Failed to create application sre-apple-apricot in AzureAD.                                                                                                                    cli.py:99
2024-04-16 11:08:44 [   ERROR]     Could not create application secret 'Apricot Authentication Secret'.                                                                                                                                                              cli.py:99
2024-04-16 11:08:44 [   ERROR]     Secret 'Apricot Authentication Secret' already exists in application 'sre-apple-apricot'.

♻️ To reproduce

Deploy, teardown and then redeploy an SRE.