Replaces abandoned #1817 and #2694
Add optional std::function callback (so it supports lambdas and normal
functions) via ::onStart, ::onEnd, ::onProgress, and ::onError methods.
Update example with their use.
From @baruch's original pull request:
The callback is called when the upgrade actually starts rather than just
the initial query so that the user can know that it will not take longer
and can also prepare for the upgrade by shutting down other works.
From @karlp's original pull request:
Incomplete: I've not updated any documentation yet. If this style looks
good, I'll happily go and update the documentation (likewise for the
examples)
Make HTTPClient take a WiFiClient parameter, allowing you to pass in a
simple HTTP WiFiClient or a BearSSL or axTLS WiFiClientSecure with
any desired verification options. Deprecate the older, TLSTraits methods.
Add basic HttpsClient example.
Add optional LED feedback to the Update class
