Reorganize models: relationship.py (domain-based) + labels.py

Move relationship input models (CascadeConfiguration, LookupAttributeMetadata,
OneToManyRelationshipMetadata, ManyToManyRelationshipMetadata) from metadata.py
into relationship.py alongside RelationshipInfo output model.

Extract Label/LocalizedLabel into labels.py.

Delete metadata.py.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tpellissier

.claude/skills/dataverse-sdk-use/SKILL.md

@@ -232,7 +232,7 @@ client.tables.delete("new_Product")
 
 #### Create One-to-Many Relationship
 ```python
-from PowerPlatform.Dataverse.models.metadata import (
+from PowerPlatform.Dataverse.models.relationship import (
     LookupAttributeMetadata,
     OneToManyRelationshipMetadata,
     Label,
@@ -264,7 +264,7 @@ print(f"Created lookup field: {result['lookup_schema_name']}")
 
 #### Create Many-to-Many Relationship
 ```python
-from PowerPlatform.Dataverse.models.metadata import ManyToManyRelationshipMetadata
+from PowerPlatform.Dataverse.models.relationship import ManyToManyRelationshipMetadata
 
 relationship = ManyToManyRelationshipMetadata(
     schema_name="new_employee_project",

README.md

@@ -317,13 +317,12 @@ client.tables.delete("new_Product")
 Create relationships between tables using the relationship API. For a complete working example, see [examples/advanced/relationships.py](https://github.com/microsoft/PowerPlatform-DataverseClient-Python/blob/main/examples/advanced/relationships.py).
 
 ```python
-from PowerPlatform.Dataverse.models.metadata import (
+from PowerPlatform.Dataverse.models.relationship import (
     LookupAttributeMetadata,
     OneToManyRelationshipMetadata,
     ManyToManyRelationshipMetadata,
-    Label,
-    LocalizedLabel,
 )
+from PowerPlatform.Dataverse.models.labels import Label, LocalizedLabel
 
 # Create a one-to-many relationship: Department (1) -> Employee (N)
 # This adds a "Department" lookup field to the Employee table