[Issue] Enable azure.yaml to specify optional deployments for services

[pamelafox]

Our situation: we have an appservice host, and if the user sets a current azd variable, we also want to deploy a functionapp for an additional microservice.

We discussed this in an internal teams thread here:
https://teams.microsoft.com/l/message/19:[email protected]/1708030654691?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=c99e8504-1250-4d95-a824-9778e0e626c7&parentMessageId=1708030654691&teamName=Azure%20Developer%20CLI%20(azd)%20Partners&channelName=General&createdTime=1708030654691

Here's a syntax that Victor suggested:

That would work perfectly for our use case.

And he even suggested that we could switch the platform (like to change between AppService and ACA):

Without this feature, I think we will end up having to use the Azure CLI for the deployment, or forcing developers to un-comment, which is quite inelegant and prone to error.

Thanks!

[jongio]

Related #3272

[ellismg]

Part of me wonders if we should try to model this as conditions on steps in a workflow (now that we are moving down that path with how up works) instead of having conditions on the actual services.

[wbreza]

Part of me wonders if we should try to model this as conditions on steps in a workflow (now that we are moving down that path with how up works) instead of having conditions on the actual services.

If represented as a workflow user could manually call azd deploy foo for each interested service in a workflow.

[codeazon]

My company needs this as well. Do you think I can do a PR using the condition design above?

[pamelafox]

For the record, we are currently "achieving" this for a public code template by having the host line commented out, asking developers to un-comment it, and also by providing a azd environment variable that turns on the relevant Bicep modules. It's not super elegant, but it's the least code approach we could find:
Azure-Samples/azure-search-openai-demo@0225f75

@codeazon I'm curious as to your company's needs, you have situations where you sometimes want to deploy to some hosts and sometimes to others? We thought that maybe such a situation was only common for public templates with disparate developers using them.