fix masterdata create

src/masterdata/schema.py

@@ -32,8 +32,8 @@ class MasterDataCreate(MasterdataBase):
     value_num: float = Field(
         ..., nullable=True, le=1_000_000_000_000_000  # 1 quadrillion
     )
-    value_str: str = Field(..., nullable=True)
+    value_str: str = Field(None, nullable=True)
-    seq: int = Field(..., nullable=True)
+    seq: int = Field(None, nullable=True)
 
 
 class MasterDataUpdate(MasterdataBase):