https_ssl_verify filter should be documented as accepting string values too

[chesio]

The https_ssl_verify filter is currently ​documented to expect and return a boolean value: whether to verify the SSL connection.

In context of WP_Http::request() call, it can be however handled a string value (path to SSL certificate bundle) too: it gets value of sslcertificates argument whenever sslverify argument is true. See lines ​355, ​359 and ​376.

It seems this is a regression introduced in [37428] where Requests library replaced custom implementation.

Sidenote: The same would apply to the "sibling" ​https_local_ssl_verify filter, but this filter is currently not executed in context of WP_Http::request() call - this seem to be a bug, see #51767.

The ​`https_ssl_verify` and ​`https_local_ssl_verify` filters are currently documented to expect and return a boolean value (whether to verify the SSL connection) and to expect a request URL.

However a string value (path to SSL certificate bundle) is often provided and when a boolean is provided, it is often false instead of true.

Furthermore, the request URL is often omitted.

See ​`WP_Site_Health::get_test_rest_availability()` for an example.

Trac ticket: https://core.trac.wordpress.org/ticket/54803

[mcaskill]

I've recently stumbled upon this issue and I've provided a pull request to fix the documentation.

[johnbillion]

In 55063:

HTTP API: Correct the documentation for the https_ssl_verify and https_local_ssl_verify filters.

The value for both these filters can also contain a string path to a CA file used to authenticate the identity of the remote server.

Props chesio, mcaskill

Fixes #54803

https://core.trac.wordpress.org/changeset/55063