feat: add user-related API endpoints and enhance issue participant retrieval

app/entities/members.py

@@ -39,3 +39,68 @@ def assign_issue(issue_id: int, assigned_to_id: int, comment: str = "") -> str:
         body["issue"]["notes"] = comment
     _put(f"/issues/{issue_id}.json", body)
     return f"Issue #{issue_id} assigned to user_id={assigned_to_id}."
+
+
+@mcp.tool()
+def unassign_issue(issue_id: int, comment: str = "") -> str:
+    """
+    Remove the assignee from a Redmine issue (set to unassigned).
+
+    Args:
+        issue_id: Redmine issue ID
+        comment:  Optional comment to add with the change
+    """
+    body: dict = {"issue": {"assigned_to_id": ""}}
+    if comment:
+        body["issue"]["notes"] = comment
+    _put(f"/issues/{issue_id}.json", body)
+    return f"Issue #{issue_id} unassigned."
+
+
+@mcp.tool()
+def get_issue_participants(issue_id: int) -> str:
+    """
+    Get all users who have participated in a Redmine issue:
+    author, current assignee, watchers, commenters, and editors.
+
+    Useful for understanding who works with a task and who wrote comments.
+    Each participant includes their roles (author, assignee, watcher,
+    commenter, editor) based on actual actions recorded in the issue history.
+
+    Args:
+        issue_id: Redmine issue ID
+    """
+    data = _get(f"/issues/{issue_id}.json", params={"include": "journals,watchers"})
+    issue = data["issue"]
+
+    participants: dict[int, dict] = {}
+
+    def _add(uid: int, uname: str, role: str) -> None:
+        if uid not in participants:
+            participants[uid] = {"id": uid, "name": uname, "roles": []}
+        if role not in participants[uid]["roles"]:
+            participants[uid]["roles"].append(role)
+
+    author = issue.get("author", {})
+    if author.get("id"):
+        _add(author["id"], author["name"], "author")
+
+    assignee = issue.get("assigned_to", {})
+    if assignee.get("id"):
+        _add(assignee["id"], assignee["name"], "assignee")
+
+    for w in issue.get("watchers", []):
+        if w.get("id"):
+            _add(w["id"], w["name"], "watcher")
+
+    for j in issue.get("journals", []):
+        user = j.get("user", {})
+        uid = user.get("id")
+        uname = user.get("name", "?")
+        if uid:
+            if j.get("notes"):
+                _add(uid, uname, "commenter")
+            if j.get("details"):
+                _add(uid, uname, "editor")
+
+    return json.dumps(list(participants.values()), ensure_ascii=False, indent=2)