## Summary of changes
### RequestMonitoring
We want to add an event stream with information on each request for
easier analysis than what we can do with diagnostic logs alone
(https://github.com/neondatabase/cloud/issues/8807). This
RequestMonitoring will keep a record of the final state of a request. On
drop it will be pushed into a queue to be uploaded.
Because this context is a bag of data, I don't want this information to
impact logic of request handling. I personally think that weakly typed
data (such as all these options) makes for spaghetti code. I will
however allow for this data to impact rate-limiting and blocking of
requests, as this does not _really_ change how a request is handled.
### Parquet
Each `RequestMonitoring` is flushed into a channel where it is converted
into `RequestData`, which is accumulated into parquet files. Each file
will have a certain number of rows per row group, and several row groups
will eventually fill up the file, which we then upload to S3.
We will also upload smaller files if they take too long to construct.
This patch aims to fix some of the inconsistencies in error reporting,
for example "Internal error" or "Console request failed" instead of
"password authentication failed for user '<NAME>'".
[proxy] Add the `password hack` authentication flow
This lets us authenticate users which can use neither
SNI (due to old libpq) nor connection string `options`
(due to restrictions in other client libraries).
Note: `PasswordHack` will accept passwords which are not
encoded in base64 via the "password" field. The assumption
is that most user passwords will be valid utf-8 strings,
and the rest may still be passed via "password_".
* [proxy] Propagate most errors to user
This change enables propagation of most errors to the user
(e.g. auth and connectivity errors). Some of them will be
stripped of sensitive information.
As a side effect, most occurrences of `anyhow::Error` were
replaced with concrete error types.
* [proxy] Box weighty errors
