I am deploying Azure Functions using bicep templates. To connect the FunctionApp to my API-Management, I want to have an additional AppKey called management that is randomly generated. Currently my solution for this looks like that

resource functionKeys 'Microsoft.Web/sites/host/functionKeys@2021-02-01' = {
  name: '${functionApp.name}/default/management'
  dependsOn: [
    functionAppConfig
  ]
  properties: {
    name: 'management'
  }
}

This worked for some weeks but now I always get the following arbitrary error when deploying the template in my DevOps Pipeline

ERROR: {"status":"Failed","error":{"code":"DeploymentFailed","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/DeployOperations for usage details.","details":[{"code":"BadRequest","message":"{\r\n  \"Code\": \"BadRequest\",\r\n  \"Message\": \"Encountered an error (ServiceUnavailable) from host runtime.\",\r\n  \"Target\": null,\r\n  \"Details\": [\r\n    {\r\n      \"Message\": \"Encountered an error (ServiceUnavailable) from host runtime.\"\r\n    },\r\n    {\r\n      \"Code\": \"BadRequest\"\r\n    },\r\n    {\r\n      \"ErrorEntity\": {\r\n        \"Code\": \"BadRequest\",\r\n        \"Message\": \"Encountered an error (ServiceUnavailable) from host runtime.\"\r\n      }\r\n    }\r\n  ],\r\n  \"Innererror\": null\r\n}"}]}}

My API-Management is available and also used by other FunctionApps successfully and the FunctionApp I try to set this key for too. In t he Azure Portal I receive an error with little more information, stating that the failed resource is of type Microsoft.Web/sites/host/functionKeys. The above mentioned code is the only occurrence of this type.

Is there any different way to properly set AppKeys for a functionApp from a Bicep template? I found Microsoft.Web/sites/functions/keys@2020-06-01 but that requires a parent of type Microsoft.Web/sites/functions but I use type Microsoft.Web/sites for my symbolic name functionApp.