The bug comes with the SQLx-sqlite pool bug, where several connections are
created by default, but the `new` function takes care of that, fixing that bug
by making a single instance of the database.
If constructed directly, the pool would create several connections to the
database, which in most instances is fine, but with SQLite :memory: each
connection is entirely independent.
Also follow documentation to make sure that failed `acquire` will not end up
dropping connections by setting test_before_acquire to false
However, if your workload is sensitive to dropped connections such as using an in-memory
SQLite database with a pool size of 1, you can pretty easily ensure that a cancelled
`acquire()` call will never drop connections by tweaking your [`PoolOptions`]:
* Set [`test_before_acquire(false)`][PoolOptions::test_before_acquire]
* Never set [`before_acquire`][PoolOptions::before_acquire] or
[`after_connect`][PoolOptions::after_connect].
The main goal is to add a subscription to CDK Mint updates into the wallet.
This feature will be particularly useful for improving the code whenever loops
hit the mint server to check status changes.
The goal is to add an easy-to-use interface that will hide the fact that we're
connecting to WebSocket and subscribing to events. This will also hide the fact
that the CDK-mint server may not support WebSocket updates.
To be fully backward compatible, the HttpClientMethods traits have a new
method, `subscribe,` which will return an object that implements
`ActiveSubscription.`
In the primary implementation, there is a `SubscriptionClient` that will
attempt to connect through WebSocket and will fall to the HTTP-status pull and
sleep approach (the current approach), but upper stream code will receive
updates as if they come from a stream of updates through WebSocket. This
`SubscriptionClient` struct will also manage reconnections to WebSockets (with
automatic resubscriptions) and all the low-level stuff, providing an
easy-to-use interface and leaving the upper-level code with a nice interface
that is hard to misuse. When `ActiveSubscription` is dropped, it will
automatically unsubscribe.
Fixed bug with Default as described in https://github.com/cashubtc/cdk/pull/473#discussion_r1871032297
