ci: type-check untyped function bodies (#320)

Author: rylinjames

pyproject.toml

@@ -329,7 +329,7 @@ python_version = "3.10"
 mypy_path = "src"
 ignore_missing_imports = true
 follow_imports = "silent"
-check_untyped_defs = false
+check_untyped_defs = true
 warn_unused_configs = true
 exclude = [
     "src/tether/models/third_party/",