graphql: Add a method to list groups

Cargo.lock

@@ -1509,6 +1509,15 @@ dependencies = [
  "cfg-if 1.0.0",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.10.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69ddb889f9d0d08a67338271fa9b62996bc788c7796a5c18cf057420aaed5eaf"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "0.4.8"
@@ -1705,6 +1714,7 @@ dependencies = [
  "futures-util",
  "hmac 0.10.1",
  "http",
+ "itertools",
  "juniper",
  "juniper_actix",
  "jwt",