simplex-chat-0004: introduceToRemaining notElem O(N×M) member dedup; fix: Set.notMember O(log N)

defects/simplex-chat/patch/simplex-chat-0004-introduce-to-remaining-notelem.patch

@@ -0,0 +1,25 @@
+# UNDF: (pending)
+--- a/src/Simplex/Chat/Library/Internal.hs
++++ b/src/Simplex/Chat/Library/Internal.hs
+@@ -30,6 +30,7 @@ import Control.Monad.Except
+ import Data.Bifunctor (bimap, first)
+ import Data.Fixed (Fixed (..))
+ import Data.List (find, foldl', mapAccumL, partition)
++import qualified Data.Set as S
+ import Data.Map.Strict (Map)
+ import qualified Data.Map.Strict as M
+ ...
+@@ -1064,9 +1064,11 @@ introduceToRemaining vr user gInfo m = do
+   (members, introducedGMIds) <-
+     withStore' $ \db -> (,) <$> getGroupMembers db vr user gInfo <*> getIntroducedGroupMemberIds db m
+-  let recipients = filter (introduceMemP introducedGMIds) members
++  let introducedSet = S.fromList introducedGMIds
++      recipients = filter (introduceMemP introducedSet) members
+   introduceMember vr user gInfo m recipients Nothing
+   where
+-    introduceMemP introducedGMIds mem =
++    introduceMemP introducedSet mem =
+       memberCurrent mem
+-        && groupMemberId' mem `notElem` introducedGMIds
++        && groupMemberId' mem `S.notMember` introducedSet
+         && groupMemberId' mem /= groupMemberId' m