"Access denied for user" when trying to access MySQL database from Azure Pipelines

Question

I'm running a MySql database on Azure. My ultimate goal is to add an AADUser to the database from a pipeline in Azure DevOps. An AADUser can only be added by the AADAdmin. So I was thinking to create an AADAdmin based on the service principal that Azure DevOps uses to connect to Azure (service connection).

I have done the following steps:

1. In the portal, lookup the objectId of the service principal that is linked to my service connection ('Unicorn Dev') in Azure DevOps.
2. Create the AADAdmin with that objectId: az mysql server ad-admin create --server-name mydb -g myrg --display-name devops_service_connection_dev@mydb --object-id d5ab6ee1-55d4-4c78-ae71-d49526310733. (I can see this user in the database after running the command). See https://learn.microsoft.com/en-us/cli/azure/mysql/server/ad-admin?view=azure-cli-latest#az_mysql_server_ad_admin_create
3. Try to connect to the database from a pipeline in Azure DevOps:

- task: AzureCLI@2
  inputs:
    azureSubscription: 'Unicorn Dev'
    scriptType: 'bash'
    scriptLocation: 'inlineScript'
    inlineScript: 'mysql -h mydb.mysql.database.azure.com --user devops_service_connection_dev@mydb --password=`az account get-access-token --resource-type oss-rdbms --output tsv --query accessToken` --ssl-ca=BaltimoreCyberTrustRoot.crt.pem --enable-cleartext-plugin;'

This command fails with the following error: ERROR 1045 (28000): Access denied for user 'devops_service_connection_dev@mydb'@'51.144.241.08' (using password: YES)

The task does generate an access token, and when running the same script with that access token in the Cloud Shell, I get the same error.

Some help would be greatly appreciated!