fix: create permission endpoint

Verifies service exists before attaching permission.

Response built manually because calculated properties are not handled by .__dict()__

Request model uses Service ID mixin.

Service ID mixin verifies ID > 0

src/service/schemas.py

@@ -6,12 +6,12 @@ Models follow the nomenclature of:
 - Mixins: "<Attribute>Mixin"
 - Models: "<Module><Method><Resource><Opt:Resource><Direction>" ie "ServiceGetServiceResponse"
 """
-from pydantic import ConfigDict
+from pydantic import ConfigDict, Field
 
 from src.schemas import CustomBaseModel
 
 class ServiceIDMixin(CustomBaseModel):
-	service_id: int
+	service_id: int = Field(gt=0)
 
 class ServiceSchema(CustomBaseModel):
 	model_config = ConfigDict(from_attributes=True, extra="ignore")