Shared Image Gallery is not supported - vm_managed_image_id

[rafamarrara]

Do we plan to allow the plugin to work with images hosted on a Shared Image Gallery?

Shared Image Gallery
https://docs.microsoft.com/en-us/azure/virtual-machines/windows/shared-image-galleries

Today we see the following error when trying to use it:

Microsoft Azure Provider:* The vm_managed_image_id doesn't fit the expected format, plese verify it looks like '/subscriptions/{sub_id}/resourceGroups/{group_name}/providers/Microsoft.Compute/images/{image_name}'

I see the regex here on managed_image_helper.rb only checking for a normal image.

For reference the format of the resource id of an image on a Shared Image Gallery is the following:

/subscriptions/{sub_id}/resourceGroups/{group_name}/providers/Microsoft.Compute/galleries/{sharedgallery_name}/images/{image_name}/versions/{version_name}

I don't believe that only changing the helper is going to solve the problem, but it may help to find all the connected parts.