Feature/nymd client integration (#736)

* Calculating gas fees

* Ability to set custom fees

* Added extra test

* Removed commented code

* Moved all msg types to common contract crate

* Temporarily disabling get_tx method

* Finishing up nymd client API

* Comment fix

* Remaining fee values

* Some cleanup

* Removed needless borrow

* Fixed imports in contract tests

* Moved error types around

* New ValidatorClient

* Experiment with new type of defaults

* Removed dead module

* Dealt with unwrap

* Migrated mixnode to use new validator client

* Migrated gateway to use new validator client

* Mixnode and gateway adjustments

* More exported defaults

* Clients using new validator client

* Fixed mixnode upgrade

* Moved default values to a new crate

* Changed behaviour of validator client features

* Migrated basic functions of validator api

* Updated config + fixed startup

* Fixed wasm client build

* Integration with the explorer api

* Removed tokio dev dependency

* Needless borrow

* Fixex wasm client build

* Fixed tauri client build

* Needless borrows

* Fixed client upgrade print

* Removed redundant comments

* Made note on aggregated verification key into a doc comment

* Removed mixnet contract references from verloc

* Modified default validators structure

* Reformatted validator-api Cargo.toml file

* Removed commented code

* Made the doc comment example a no-run

* Fixed a upgrade print... again

* Adjusted the doc example

* Removed unused import

validator-api/src/network_monitor/mod.rs

@@ -15,8 +15,12 @@ use crate::network_monitor::monitor::summary_producer::SummaryProducer;
 use crate::network_monitor::monitor::Monitor;
 use crate::network_monitor::tested_network::TestedNetwork;
 use crate::storage::NodeStatusStorage;
+use coconut_interface::Credential;
+use credentials::bandwidth::prepare_for_spending;
+use credentials::obtain_aggregate_verification_key;
 use crypto::asymmetric::{encryption, identity};
 use futures::channel::mpsc;
+use log::info;
 use nymsphinx::addressing::clients::Recipient;
 use std::sync::Arc;
 use topology::NymTopology;
@@ -44,7 +48,7 @@ impl NetworkMonitorRunnables {
     }
 }
 
-pub(crate) fn new_monitor_runnables(
+pub(crate) async fn new_monitor_runnables(
     config: &Config,
     v4_topology: NymTopology,
     v6_topology: NymTopology,
@@ -86,10 +90,14 @@ pub(crate) fn new_monitor_runnables(
         *encryption_keypair.public_key(),
     );
 
+    let bandwidth_credential =
+        TEMPORARY_obtain_bandwidth_credential(config, identity_keypair.public_key()).await;
+
     let packet_sender = new_packet_sender(
         config,
         gateway_status_update_sender,
         Arc::clone(&identity_keypair),
+        bandwidth_credential,
         config.get_gateway_sending_rate(),
     );
 
@@ -135,15 +143,44 @@ fn new_packet_preparer(
     )
 }
 
+// SECURITY:
+// this implies we are re-using the same credential for all gateways all the time (which unfortunately is true!)
+#[allow(non_snake_case)]
+async fn TEMPORARY_obtain_bandwidth_credential(
+    config: &Config,
+    identity: &identity::PublicKey,
+) -> Credential {
+    info!("Trying to obtain bandwidth credential...");
+    let validators = config.get_all_validator_api_endpoints();
+
+    let verification_key = obtain_aggregate_verification_key(&validators)
+        .await
+        .expect("could not obtain aggregate verification key of ALL validators");
+
+    let bandwidth_credential =
+        credentials::bandwidth::obtain_signature(&identity.to_bytes(), &validators)
+            .await
+            .expect("failed to obtain bandwidth credential!");
+
+    prepare_for_spending(
+        &identity.to_bytes(),
+        &bandwidth_credential,
+        &verification_key,
+    )
+    .expect("failed to prepare bandwidth credential for spending!")
+}
+
 fn new_packet_sender(
     config: &Config,
     gateways_status_updater: GatewayClientUpdateSender,
     local_identity: Arc<identity::KeyPair>,
+    bandwidth_credential: Credential,
     max_sending_rate: usize,
 ) -> PacketSender {
     PacketSender::new(
         gateways_status_updater,
         local_identity,
+        bandwidth_credential,
         config.get_gateway_response_timeout(),
         config.get_gateway_connection_timeout(),
         config.get_max_concurrent_gateway_clients(),