feat: Make `equipment_master` field optional in `EquipmentDataMaster` schema.

src/equipment/schema.py

@@ -127,7 +127,7 @@ class EquipmentTop10Pagination(Pagination):
 
 class EquipmentDataMaster(EquipmentBase):
     id: UUID
-    equipment_master: EquipmentMasterBase
+    equipment_master: Optional[EquipmentMasterBase] = Field(None, nullable=True)
     forecasting_target_year: Optional[int] = Field(None, nullable=True)
     minimum_eac_seq: Optional[int] = Field(None, nullable=True)
     minimum_eac_year: Optional[int] = Field(None, nullable=True)