Add support for 'ref' annotation

[nimrodshn]

What this does?

Adds support for a reference directive - @ref(name="/path/to/service") in order to share resources and definitions between services.

Currently this is only supported for types in order to share their definition between services, however, as we continue to implement the /aro_hcp service we will likely enhance this implementation.

Here is an example use case where we share the Cluster type:

@ref(path = "/clusters_mgmt/v1/cluster")
class Cluster {
}

With sdk that looks like the following:

It("Check for duplicate cluster name with same Azure Resource Name", func() {
	postBody, err := arohcphelper.GetAroHCPClusterBuilder(azureBuilder, westUs3, properties).Build()
	helper.CheckError(err)
	postResponse, err := connection.AroHCP().V1Alpha1().Clusters().Add().Body(postBody).SendContext(ctx)
	helper.CheckErrorResponse(postResponse, err, http.StatusBadRequest)
	Expect(postResponse.Error().Reason()).To(ContainSubstring("Duplicate ARO-HCP cluster"))
})

Important detail is that this preserves the "links" or references to other resources unless defined explicitly, for example:

func GetAroHCPClusterBuilder(azureBuilder *arohcp.AzureBuilder,
	region string, properties map[string]string) *arohcp.ClusterBuilder {
	return arohcp.NewCluster().
		Name(helper.GenerateClusterName()).
		Product(cmv1.NewProduct().ID(models.AROProductID)).
		CCS(arohcp.NewCCS().Enabled(true)).
		Region(cmv1.NewCloudRegion().ID(region)).
		Hypershift(arohcp.NewHypershift().Enabled(true)).
		MultiAZ(true).
		Azure(azureBuilder).
		Properties(properties)
}

From the docs [committed here]:

Class references using @ref annotation

One can define a class reference inside a service such that it will inherit its content from
another service using the special @ref annotation, for example:

// In /aro_hcp/v1_alpha1/cluster_type.model
@ref(path = "/clusters_mgmt/v1/cluster")
class Cluster {
}

The above decelaration will inherit its content from the Cluster class under the /clusters_mgmt/v1 service.
This means that any changes made in Cluster class will be reflected under this derived type as well.

Links to other resources are preserved as they are.

If one wishes to override a type she can create a class inside /aro_hcp/v1_alpha1/ in order to override any nested types defined.
For example the following type declaration will override the NodePools link inside Cluster under /aro_hcp/v1:

// In /aro_hcp/v1_alpha1/node_pool_type.model
@ref(path = "/clusters_mgmt/v1/node_pool")
class NodePool {
}

This means that now under Cluster the NodePools field type is linked to the one defined in /aro_hcp/v1_alpha1 (i.e. v1alpha.NodePool) which itself references and derived from the NodePool type under /clusters_mgmt/v1.

[zgalor]

LGTM, but would like to have more eyes on this
@tzvatot @miguelsorianod

[tzvatot]

It seems that the "ref" value is mixing the URL endpoint (@ref(path = "/clusters_mgmt/v1/cluster")) with the struct definition. Same struct can be shared on different endpoint.

How about to make the path binded to the actual class definition path, rather than the endpoint itself, which can change.

[nimrodshn]

@tzvatot You're correct. This implementation is somewhat naive, we are now enhancing this mechanism to bind the struct like you suggested.

[nimrodshn]

@tzvatot PTAL - I've changed the implementation as per you're suggestion. You can see in the here a fully working example.

[tzvatot]

Please add UT

[zgalor]

lgtm

[ahitacat]

lgtm

[nimrodshn]

@jhernand Mind merging please?

[jhernand]

@jhernand Mind merging please?

Done, and you should have permissions now.

[nimrodshn]

Many thanks @jhernand !