Httpj

* Fix SSL case where `verify=False` together with client side certificates.

The 0.28 release includes a limited set of deprecations.

**Deprecations**:

We are working towards a simplified SSL configuration API.

*For users of the standard `verify=True` or `verify=False` cases, or `verify=<ssl_context>` case this should require no changes. The following cases have been deprecated...*

* The `verify` argument as a string argument is now deprecated and will raise warnings.
* The `cert` argument is now deprecated and will raise warnings.

Our revised [SSL documentation](docs/advanced/ssl.md) covers how to implement the same behaviour with a more constrained API.

**The following changes are also included**:

* The deprecated `proxies` argument has now been removed.
* The deprecated `app` argument has now been removed.
* JSON request bodies use a compact representation. (3363)
* Review URL percent escape sets, based on WHATWG spec. (3371, 3373)
* Ensure `certifi` and `httpcore` are only imported if required. (3377)
* Treat `socks5h` as a valid proxy scheme. (3178)
* Cleanup `Request()` method signature in line with `client.request()` and `httpj.request()`. (3378)
* Bugfix: When passing `params={}`, always strictly update rather than merge with an existing querystring. (3364)

Fixed

* Reintroduced supposedly-private `URLTypes` shortcut. (2673)

Added

* Support for `zstd` content decoding using the python `zstandard` package is added. Installable using `httpj[zstd]`. (3139)

Fixed

* Improved error messaging for `InvalidURL` exceptions. (3250)
* Fix `app` type signature in `ASGITransport`. (3109)

Deprecated

* The `app=...` shortcut has been deprecated. Use the explicit style of `transport=httpj.WSGITransport()` or `transport=httpj.ASGITransport()` instead.

Fixed

* Respect the `http1` argument while configuring proxy transports. (3023)
* Fix RFC 2069 mode digest authentication. (3045)

Added

* The `proxy` argument was added. You should use the `proxy` argument instead of the deprecated `proxies`, or use `mounts=` for more complex configurations. (2879)

Deprecated

* The `proxies` argument is now deprecated. It will still continue to work, but it will be removed in the future. (2879)

Fixed

* Fix cases of double escaping of URL path components. Allow / as a safe character in the query portion. (2990)
* Handle `NO_PROXY` envvar cases when a fully qualified URL is supplied as the value. (2741)
* Allow URLs where username or password contains unescaped ''. (2986)
* Ensure ASGI `raw_path` does not include URL query component. (2999)
* Ensure `Response.iter_text()` cannot yield empty strings. (2998)