Support the Relations editor for multiple selected features (close #7753)

data/core.yaml

@@ -73,7 +73,9 @@ en:
     cancel_draw:
       annotation: Canceled drawing.
     change_role:
-      annotation: Changed the role of a relation member.
+      annotation:
+        one: Changed the role of a relation member.
+        other: "Changed the roles of {n} relation members."
     change_tags:
       annotation: Changed tags.
     copy:
@@ -242,9 +244,13 @@ en:
         single: This feature can't be downgraded because it has a Wikidata tag.
         multiple: These features can't be downgraded because some have Wikidata tags.
     add_member:
-      annotation: Added a member to a relation.
+      annotation:
+        one: Added a member to a relation.
+        other: "Added {n} members to a relation."
     delete_member:
-      annotation: Removed a member from a relation.
+      annotation:
+        one: Removed a member from a relation.
+        other: "Removed {n} members from a relation."
     reorder_members:
       annotation: Reordered a relation's members.
     connect:
@@ -683,6 +689,7 @@ en:
     new_relation: New relation...
     choose_relation: Choose a parent relation
     role: Role
+    multiple_roles: Multiple Roles
     choose: Select feature type
     results:
       one: "{n} result for {search}"