Record usage of client type in metrics

[jpraynaud]

Why

We want to record the usage of the different types of Mithril clients in the metrics that we record.

What

Provide automatic recording of the type of Mithril client used to call the aggregator in the metrics.

How

• Create a list of authorized client types:
  • Fully hard-coded: CLI, WASM, LIBRARY, NA
• In the client library:
  • Set a specific option for the client type:
    • defaults to LIBRARY
    • use a an enum for the values (undocumented with #[doc(hidden)])
    • create a with_client_type function in the ClientBuilder
  • Add a new mithril-client-type HTTP header to the calls made to aggregator with the value of this option
• In the client CLI, use the client type CLI when building the client
• In the client WASM, use the client type WASM when building the client
• In the aggregator, add a middleware to the HTTP routes for computing the client type:
  • If it is not set or unknown, then fallback to NA
  • Use the received client type in the metrics recording inside the handlers of the routes
  • Update EventMessage with the client type when needed
• In the aggregator, extend the metrics:
  • Support recording of a metric with a client type
  • Update all the calls to the metrics to support an optional client type
  • In the state machine, the calls to the metrics should not be modified (as there is no client type in that case)
• Adapt the UsageReporter to send the client type in the event stored in the event store
• Create a new migration in the event store database of the aggregator and add a new metrics_per_day_and_client_type view

Later

• Adapt the Grafana dashboard