Add RPC to batch retrieve gateway connection stats

[KrishnaIyer]

Summary

Closes #5398

Changes

• Add new BatchGetGatewayConnectionStats.
• Implement GS registry interface
• Add CLI support

Testing

• UT
• E2E

End to End test with two (simulated) gateways
----------------------------------------------

1. Gateways not created

$./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
error:pkg/identityserver/gormstore:gateway_not_found (gateway `test-gtw-1` not found)
    gateway_id=test-gtw-1
    correlation_id=2905f102c2aa498aaa53223bd22dcf30

2. Gateways created but not connected

$ ./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{}

3. Gateway 1 connected

$./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "connected_at": "2022-07-13T11:44:14.364400Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}

4. Both gateways connected

$ ./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "connected_at": "2022-07-13T11:44:14.364400Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    },
    "test-gtw-1": {
      "connected_at": "2022-07-13T11:44:34.619971Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}


5. Gateway 2 disconnected

$ ./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "connected_at": "2022-07-13T11:44:14.364400Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    },
    "test-gtw-1": {
      "disconnected_at": "2022-07-13T11:44:45.462092Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}

6. Gateway 1 disconnected

$ ./ttn-lw-cli gtw get-connection-stats test-gtw-2 --gateway-ids test-gtw,test-gtw-1
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "disconnected_at": "2022-07-13T11:44:49.544901Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    },
    "test-gtw-1": {
      "disconnected_at": "2022-07-13T11:44:45.462092Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}


7. Regression

$ ./ttn-lw-cli gtw get-connection-stats test-gtw
WARN    Using insecure connection to OAuth server
WARN    Using insecure connection to API
{
  "disconnected_at": "2022-07-13T11:44:49.544901Z",
  "protocol": "ws",
  "gateway_remote_address": {
    "ip": "127.0.0.1"
  }
}


8. Filter on paths

./ttn-lw-cli gtw get-connection-stats --gateway-ids test-gtw,test-gtw-1 --paths protocol
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "protocol": "ws"
    },
    "test-gtw-1": {
      "protocol": "ws"
    }
  }
}

$ ./ttn-lw-cli gtw get-connection-stats --gateway-ids test-gtw,test-gtw-1 --paths protocol,disconnected_at
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "disconnected_at": "2022-07-13T11:44:49.544901Z",
      "protocol": "ws"
    },
    "test-gtw-1": {
      "disconnected_at": "2022-07-13T11:44:45.462092Z",
      "protocol": "ws"
    }
  }
}


9. Check invalid paths
 
./ttn-lw-cli gtw get-connection-stats --gateway-ids test-gtw,test-gtw-1 --paths protocol,disconnected_at,wrong_path
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
error:pkg/rpcmiddleware/validator:field_mask_paths (forbidden path(s) in field mask)
    forbidden_paths=[wrong_path]
    correlation_id=ceebc010321842b4b35f310f67db2b98

Regressions

Possible regression in get-connection-stats CLI command. Test case 7 covers this.

Checklist

• Scope: The referenced issue is addressed, there are no unrelated changes.
• Compatibility: The changes are backwards compatible with existing API, storage, configuration and CLI, according to the compatibility commitments in README.md for the chosen target branch.
• Documentation: Relevant documentation is added or updated.
• Changelog: Significant features, behavior changes, deprecations and fixes are added to CHANGELOG.md.
• Commits: Commit messages follow guidelines in CONTRIBUTING.md, there are no fixup commits left.

[adriansmares]

Cool, now it is really clean.

[johanstokking]

Looks good but few questions

[KrishnaIyer]

Test for CLI Combinations

$ ./ttn-lw-cli gtw get-connection-stats test-gtw
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "disconnected_at": "2022-07-13T11:44:49.544901Z",
  "protocol": "ws",
  "gateway_remote_address": {
    "ip": "127.0.0.1"
  }
}


$ ./ttn-lw-cli gtw get-connection-stats --gateway-id test-gtw
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "disconnected_at": "2022-07-13T11:44:49.544901Z",
  "protocol": "ws",
  "gateway_remote_address": {
    "ip": "127.0.0.1"
  }
}

$ ./ttn-lw-cli gtw get-connection-stats --gateway-ids test-gtw
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "disconnected_at": "2022-07-13T11:44:49.544901Z",
  "protocol": "ws",
  "gateway_remote_address": {
    "ip": "127.0.0.1"
  }
}


$ ./ttn-lw-cli gtw get-connection-stats --gateway-ids test-gtw,test-gtw-1
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "disconnected_at": "2022-07-13T11:44:49.544901Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    },
    "test-gtw-1": {
      "disconnected_at": "2022-07-13T11:44:45.462092Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}

$ ./ttn-lw-cli gtw get-connection-stats test-gtw test-gtw-1
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
{
  "entries": {
    "test-gtw": {
      "disconnected_at": "2022-07-13T11:44:49.544901Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    },
    "test-gtw-1": {
      "disconnected_at": "2022-07-13T11:44:45.462092Z",
      "protocol": "ws",
      "gateway_remote_address": {
        "ip": "127.0.0.1"
      }
    }
  }
}


$ ./ttn-lw-cli gtw get-connection-stats
WARN  Using insecure connection to OAuth server
WARN  Using insecure connection to API
error:cmd/ttn-lw-cli/commands:no_gateway_id (no gateway ID set)
    correlation_id=640a684b72354a5b93db492076374666