view-user: add --list-banks option

Problem: There is no concise way to view the banks that a user belongs
to.

Add a --list-banks optional argument to view-user, which will just print
the banks that a user belongs to in the flux-accounting database.

src/bindings/python/fluxacct/accounting/user_subcommands.py

@@ -286,9 +286,19 @@ def clear_queues(conn, username, bank=None):
 #                   Subcommand Functions                      #
 #                                                             #
 ###############################################################
-def view_user(conn, user, parseable=False, json_fmt=False):
+def view_user(conn, user, parseable=False, json_fmt=False, list_banks=False):
     cur = conn.cursor()
     try:
+        if list_banks:
+            # just return the list of banks a user belongs to
+            cur.execute("SELECT bank FROM association_table WHERE username=?", (user,))
+            result = cur.fetchall()
+            banks = ""
+            for bank in result:
+                banks += f"{str(bank[0])}\n"
+
+            return banks
+
         # get the information pertaining to a user in the DB
         cur.execute("SELECT * FROM association_table where username=?", (user,))
         result = cur.fetchall()

src/cmd/flux-account-service.py

@@ -149,6 +149,7 @@ def view_user(self, handle, watcher, msg, arg):
                 msg.payload["username"],
                 msg.payload["parseable"],
                 msg.payload["json"],
+                msg.payload["list_banks"],
             )
 
             payload = {"view_user": val}

src/cmd/flux-account.py

@@ -53,6 +53,13 @@ def add_view_user_arg(subparsers):
         help="print all information of an association in JSON format",
         metavar="JSON",
     )
+    subparser_view_user.add_argument(
+        "--list-banks",
+        action="store_const",
+        const=True,
+        help="list all of the banks a user belongs to",
+        metavar="LIST_BANKS",
+    )
 
 
 def add_add_user_arg(subparsers):
@@ -654,6 +661,7 @@ def select_accounting_function(args, output_file, parser):
             "username": args.username,
             "parseable": args.parseable,
             "json": args.json,
+            "list_banks": args.list_banks,
         }
         return_val = flux.Flux().rpc("accounting.view_user", data).get()
     elif args.func == "add_user":