fixes #5679 - create model lookup for compute_resource_name association to work

@domcleal, after reading the issue #5679, the core issue is the method `resource_identifying_attributes` that is used in `find_resource` in `base_controller.rb`. It only uses the `resource_identifying_attributes` of the current controller even to find nested objects (which may have different `resource_identifying_attributes`). This is why I wanted to simplify the find methods and have the same logic between UI and API.

Friendly_id gem will let me do this
```ruby 
ComputeResource.find('ec2-eu')
```
I could implement the `to_label` as a slug so this works
```ruby 
ComputeResource.find("ec2-eu (eu-west-1-EC2)")
```
but I think it's unneccessary since `name` is unique.