ipn/ipnlocal: populate Groups field in profileFromView

This populates UserProfile.Groups in the WhoIs response from the
local backend with the groups of the corresponding user in the
netmap.

This allows tsnet apps to see (and e.g. forward) which groups a
user making a request belongs to - as long as the tsnet app runs
on a node that been granted the tailscale.com/visible-groups
capability via node attributes. If that's not the case or the
user doesn't belong to any groups allow-listed via the node
attribute, Groups won't be populated.

Updates tailscale/corp#31529

Signed-off-by: Gesa Stupperich <gesa@tailscale.com>

ipn/ipnlocal/local.go

@@ -1473,6 +1473,7 @@ func profileFromView(v tailcfg.UserProfileView) tailcfg.UserProfile {
 			LoginName:     v.LoginName(),
 			DisplayName:   v.DisplayName(),
 			ProfilePicURL: v.ProfilePicURL(),
+			Groups:        v.Groups().AsSlice(),
 		}
 	}
 	return tailcfg.UserProfile{}

ipn/ipnlocal/local_test.go

@@ -2070,19 +2070,21 @@ func TestWhoIs(t *testing.T) {
 			}).View(),
 			20: (&tailcfg.UserProfile{
 				DisplayName: "Peer",
+				Groups:      []string{"group:foo"},
 			}).View(),
 		},
 	})
 	tests := []struct {
-		q        string
-		want     tailcfg.NodeID // 0 means want ok=false
-		wantName string
+		q          string
+		want       tailcfg.NodeID // 0 means want ok=false
+		wantName   string
+		wantGroups []string
 	}{
-		{"100.101.102.103:0", 1, "Myself"},
-		{"100.101.102.103:123", 1, "Myself"},
-		{"100.200.200.200:0", 2, "Peer"},
-		{"100.200.200.200:123", 2, "Peer"},
-		{"100.4.0.4:404", 0, ""},
+		{"100.101.102.103:0", 1, "Myself", nil},
+		{"100.101.102.103:123", 1, "Myself", nil},
+		{"100.200.200.200:0", 2, "Peer", []string{"group:foo"}},
+		{"100.200.200.200:123", 2, "Peer", []string{"group:foo"}},
+		{"100.4.0.4:404", 0, "", nil},
 	}
 	for _, tt := range tests {
 		t.Run(tt.q, func(t *testing.T) {
@@ -2097,6 +2099,9 @@ func TestWhoIs(t *testing.T) {
 			if up.DisplayName != tt.wantName {
 				t.Errorf("got name %q; want %q", up.DisplayName, tt.wantName)
 			}
+			if !slices.Equal(up.Groups, tt.wantGroups) {
+				t.Errorf("got groups %q; want %q", up.Groups, tt.wantGroups)
+			}
 		})
 	}
 }