lib.ExecContext.username: Add property

Add the property .username, backed by the protected _username()
callback. It should return the user run()'s cmd parameter is executed
as.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ec/Local.py

@@ -2,6 +2,8 @@
 
 import os, sys, subprocess, asyncio, pwd, grp, stat
 
+from functools import cache
+
 from ..ExecContext import ExecContext as Base
 from ..base import Result, StatResult
 
@@ -13,6 +15,10 @@ class Local(Base):
     def __init__(self, uri='local', *args, **kwargs) -> None:
         super().__init__(uri, *args, **kwargs)
 
+    @cache
+    def _username(self) -> str:
+        return pwd.getpwuid(os.getuid()).pw_name,
+
     async def _run(
         self,
         cmd: list[str],