core.common: move listify to core.utils.itertools, use better typing annotations for it

also some minor refactoring of my.rss

my/rss/feedly.py

@@ -1,14 +1,15 @@
 """
 Feedly RSS reader
 """
+
 from my.config import feedly as config
 
 from datetime import datetime, timezone
 import json
 from pathlib import Path
-from typing import Iterable, Sequence
+from typing import Iterator, Sequence
 
-from ..core.common import listify, get_files
+from my.core import get_files
 from .common import Subscription, SubscriptionState
 
 
@@ -16,13 +17,12 @@ def inputs() -> Sequence[Path]:
     return get_files(config.export_path)
 
 
-@listify
-def parse_file(f: Path):
+def parse_file(f: Path) -> Iterator[Subscription]:
     raw = json.loads(f.read_text())
     for r in raw:
         # err, some even don't have website..
         rid = r['id']
-        website = r.get('website', rid) # meh
+        website = r.get('website', rid)  # meh
         yield Subscription(
             created_at=None,
             title=r['title'],
@@ -31,9 +31,9 @@ def parse_file(f: Path):
         )
 
 
-def states() -> Iterable[SubscriptionState]:
+def states() -> Iterator[SubscriptionState]:
     for f in inputs():
         dts = f.stem.split('_')[-1]
         dt = datetime.strptime(dts, '%Y%m%d%H%M%S').replace(tzinfo=timezone.utc)
-        subs = parse_file(f)
+        subs = list(parse_file(f))
         yield dt, subs