fix: apply expanduser to dotenv_path (#525)

Apply os.path.expanduser() / Path.expanduser() to dotenv_path so that
~ is properly expanded to the user's home directory. The fix preserves
the original type (str stays str, Path stays Path) and is applied in
DotEnv.__init__, set_key, and unset_key.

Author: veeceey

src/dotenv/main.py

@@ -53,6 +53,10 @@ def __init__(
         override: bool = True,
     ) -> None:
         self.dotenv_path: Optional[StrPath] = dotenv_path
+        if isinstance(dotenv_path, str):
+            self.dotenv_path = os.path.expanduser(dotenv_path)
+        elif dotenv_path is not None:
+            self.dotenv_path = pathlib.Path(dotenv_path).expanduser()
         self.stream: Optional[IO[str]] = stream
         self._dict: Optional[Dict[str, Optional[str]]] = None
         self.verbose: bool = verbose
@@ -174,6 +178,10 @@ def set_key(
     If the .env path given doesn't exist, fails instead of risking creating
     an orphan .env somewhere in the filesystem
     """
+    if isinstance(dotenv_path, str):
+        dotenv_path = os.path.expanduser(dotenv_path)
+    else:
+        dotenv_path = pathlib.Path(dotenv_path).expanduser()
     if quote_mode not in ("always", "auto", "never"):
         raise ValueError(f"Unknown quote_mode: {quote_mode}")
 
@@ -220,6 +228,10 @@ def unset_key(
     If the .env path given doesn't exist, fails.
     If the given key doesn't exist in the .env, fails.
     """
+    if isinstance(dotenv_path, str):
+        dotenv_path = os.path.expanduser(dotenv_path)
+    else:
+        dotenv_path = pathlib.Path(dotenv_path).expanduser()
     if not os.path.exists(dotenv_path):
         logger.warning("Can't delete from %s - it doesn't exist.", dotenv_path)
         return None, key_to_unset