feat: Type object hashing (#203)

Author: ptiurin

src/firebolt/async_db/_types.py

@@ -120,6 +120,9 @@ def __init__(self, precision: int, scale: int):
     def __str__(self) -> str:
         return f"Decimal({self.precision}, {self.scale})"
 
+    def __hash__(self) -> int:
+        return hash(str(self))
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, DECIMAL):
             return NotImplemented
@@ -137,6 +140,9 @@ def __init__(self, precision: int):
     def __str__(self) -> str:
         return f"DateTime64({self.precision})"
 
+    def __hash__(self) -> int:
+        return hash(str(self))
+
     def __eq__(self, other: object) -> bool:
         if not isinstance(other, DATETIME64):
             return NotImplemented