feat(videochat): implement LiveKit integration for video chat functionality

- Add LiveKit client setup and token generation for room access.
- Implement room management functions including CreateRoom, OpenRoom, ListRooms, and DeleteRoom.
- Introduce participant management with ListParticipants and RemoveParticipant functions.
- Create tests for room and participant management, ensuring proper authentication and authorization.
- Add error handling for LiveKit API interactions.
- Define data structures for room metadata and token responses.
- Implement status endpoint for service availability check.

videochat/participants.go

@@ -0,0 +1,84 @@
+package videochat
+
+import (
+	"context"
+	"strings"
+
+	"encore.dev/beta/auth"
+	"encore.dev/beta/errs"
+	"github.com/livekit/protocol/livekit"
+)
+
+type Participant struct {
+	SID      string `json:"sid"`
+	Identity string `json:"identity"`
+	Name     string `json:"name"`
+	State    string `json:"state"`
+}
+
+type ListParticipantsResponse struct {
+	Participants []*Participant `json:"participants"`
+}
+
+// ListParticipants lists participants in a room. Requires the room owner.
+//
+//encore:api auth method=GET path=/videochat/rooms/:roomName/participants
+func ListParticipants(ctx context.Context, roomName string) (*ListParticipantsResponse, error) {
+	if _, ok := auth.UserID(); !ok {
+		return nil, &errs.Error{Code: errs.Unauthenticated, Message: "must be logged in"}
+	}
+	if err := validateRoomName(roomName); err != nil {
+		return nil, err
+	}
+	client, _, err := liveKitClient()
+	if err != nil {
+		return nil, err
+	}
+	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
+	defer cancel()
+	if err := requireRoomOwner(ctx, client, roomName); err != nil {
+		return nil, err
+	}
+	result, err := client.ListParticipants(ctx, &livekit.ListParticipantsRequest{Room: roomName})
+	if err != nil {
+		return nil, liveKitError(err)
+	}
+	response := &ListParticipantsResponse{Participants: make([]*Participant, 0, len(result.Participants))}
+	for _, p := range result.Participants {
+		response.Participants = append(response.Participants, &Participant{
+			SID: p.Sid, Identity: p.Identity, Name: p.Name, State: p.State.String(),
+		})
+	}
+	return response, nil
+}
+
+// RemoveParticipant disconnects a participant. Requires the room owner.
+// It does not ban the user from requesting another token.
+//
+//encore:api auth method=DELETE path=/videochat/rooms/:roomName/participants/:identity
+func RemoveParticipant(ctx context.Context, roomName, identity string) error {
+	if _, ok := auth.UserID(); !ok {
+		return &errs.Error{Code: errs.Unauthenticated, Message: "must be logged in"}
+	}
+	if err := validateRoomName(roomName); err != nil {
+		return err
+	}
+	if strings.TrimSpace(identity) == "" {
+		return &errs.Error{Code: errs.InvalidArgument, Message: "participant identity is required"}
+	}
+	client, _, err := liveKitClient()
+	if err != nil {
+		return err
+	}
+	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
+	defer cancel()
+	if err := requireRoomOwner(ctx, client, roomName); err != nil {
+		return err
+	}
+	uid, _ := auth.UserID()
+	if identity == string(uid) {
+		return &errs.Error{Code: errs.InvalidArgument, Message: "owner cannot remove themselves; leave or close the room instead"}
+	}
+	_, err = client.RemoveParticipant(ctx, &livekit.RoomParticipantIdentity{Room: roomName, Identity: identity})
+	return liveKitError(err)
+}