CloudFormation, Logs: Resolve LogGroup physical id and attributes (#6125)

* CloudFormation, Logs: Add physical_resource_id to LogGroup

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-logs-loggroup.html#aws-resource-logs-loggroup-return-values

This brings CloudFormation's Ref behavior more in line with actual
AWS behavior. Previously, it returned an instance of a LogGroup model.

I didn't add a test case for this but I'm happy to do so if requested.

* Resolve LogGroup Fn::GetAtt

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-logs-loggroup.html#aws-resource-logs-loggroup-return-values

* Add type annotations

* Add return type annotation

* Updating CloudFormation coverage

CLOUDFORMATION_COVERAGE.md

@@ -272,8 +272,7 @@
    - [x] create implemented
    - [ ] update implemented
    - [ ] delete implemented
-   - [ ] Fn::GetAtt implemented
-      - [ ] Arn
+   - [x] Fn::GetAtt implemented
 - AWS::RDS::DBParameterGroup:
    - [x] create implemented
    - [ ] update implemented

moto/logs/models.py

@@ -306,6 +306,23 @@ class LogGroup(CloudFormationModel):
             resource_name, tags, **properties
         )
 
+    @classmethod
+    def has_cfn_attr(cls, attr: str) -> bool:
+        return attr in [
+            "Arn",
+        ]
+
+    def get_cfn_attribute(self, attribute_name: str) -> str:
+        from moto.cloudformation.exceptions import UnformattedGetAttTemplateException
+
+        if attribute_name == "Arn":
+            return self.arn
+        raise UnformattedGetAttTemplateException()
+
+    @property
+    def physical_resource_id(self) -> str:
+        return self.name
+
     def create_log_stream(self, log_stream_name: str) -> None:
         if log_stream_name in self.streams:
             raise ResourceAlreadyExistsException()