feat: schema mixins moved to project level

Resolves circular dependency issues.

src/service/schemas.py

@@ -3,17 +3,12 @@ Pydantic models for service module
 
 Models follow the nomenclature of:
 - Sub-models: "<Resource><Opt:>Schema"
-- Mixins: "<Attribute>Mixin"
 - Models: "<Module><Method><Resource><Opt:Resource><Direction>" ie "ServiceGetServiceResponse"
 """
 
-from pydantic import ConfigDict, Field
+from pydantic import ConfigDict
 
-from src.schemas import CustomBaseModel
-
-
-class ServiceIDMixin(CustomBaseModel):
-	service_id: int = Field(gt=0)
+from src.schemas import CustomBaseModel, ServiceIDMixin
 
 
 class ServiceSchema(CustomBaseModel):