addrs: Implement Equal for resource address types

This is primarily to get good default behavior for test helpers that do
deep comparison of values, but may also be convenient elsewhere.

addrs/resource.go

@@ -28,6 +28,10 @@ func (r Resource) String() string {
 	}
 }
 
+func (r Resource) Equal(other Resource) bool {
+	return r.String() == other.String()
+}
+
 // Instance produces the address for a specific instance of the receiver
 // that is idenfied by the given key.
 func (r Resource) Instance(key InstanceKey) ResourceInstance {
@@ -86,6 +90,10 @@ func (r ResourceInstance) String() string {
 	return r.Resource.String() + r.Key.String()
 }
 
+func (r ResourceInstance) Equal(other ResourceInstance) bool {
+	return r.String() == other.String()
+}
+
 // Absolute returns an AbsResourceInstance from the receiver and the given module
 // instance address.
 func (r ResourceInstance) Absolute(module ModuleInstance) AbsResourceInstance {
@@ -149,6 +157,10 @@ func (r AbsResource) String() string {
 	return fmt.Sprintf("%s.%s", r.Module.String(), r.Resource.String())
 }
 
+func (r AbsResource) Equal(other AbsResource) bool {
+	return r.String() == other.String()
+}
+
 // AbsResourceInstance is an absolute address for a resource instance under a
 // given module path.
 type AbsResourceInstance struct {
@@ -204,6 +216,10 @@ func (r AbsResourceInstance) String() string {
 	return fmt.Sprintf("%s.%s", r.Module.String(), r.Resource.String())
 }
 
+func (r AbsResourceInstance) Equal(other AbsResourceInstance) bool {
+	return r.String() == other.String()
+}
+
 // Less returns true if the receiver should sort before the given other value
 // in a sorted list of addresses.
 func (r AbsResourceInstance) Less(o AbsResourceInstance) bool {