add missing import to model template (#1072)

My first pull request in this repo. I'm still learning the UTs. 
I found that if I have a literal with a default value, the code uses
cast without importing it from typing.

I'm still learning the UTs on this. Do you think I should open an issue?

---------

Co-authored-by: Dylan Anthony <[email protected]>
Co-authored-by: Dylan Anthony <[email protected]>

Author: dorcohe

.changeset/add_missing_cast_import_when_using_const.md

@@ -0,0 +1,7 @@
+---
+default: patch
+---
+
+# Add missing `cast` import when using `const`
+
+Fixed by PR #1072. Thanks @dorcohe!

.gitignore

@@ -24,6 +24,9 @@ dmypy.json
 # JetBrains
 .idea/
 
+# Visual Studio Code
+.vscode/
+
 test-reports/
 
 /coverage.xml

openapi_python_client/parser/properties/const.py

@@ -115,6 +115,6 @@ def get_imports(self, *, prefix: str) -> set[str]:
         if self.required:
             return {"from typing import Literal"}
         return {
-            "from typing import Literal, Union",
+            "from typing import Literal, Union, cast",
             f"from {prefix}types import UNSET, Unset",
         }