instead of reading the main config's powermeter struct(s), the
individual power meters now are instanciated using a copy of their
respective config. this allows to instanciate different power meters
with different configs. as a first step, this simplifies instanciating
power meters for test purposes.
the parameters to peform an HTTP request by the HTTP(S)+JSON power meter
have been generalized by introducing a new config struct. this is now
used for all values which the HTTP(S)+JSON power meter can retrieve, and
also used by the HTTP+SML power meter implementation. we anticipate that
other feature will use this config as well.
generalizing also allows to share serialization and deserialization
methods in the configuration handler and the web API handler, leading to
de-duplication of code and reduced flash memory usage.
a new web UI component is implemented to manage a set of HTTP request
settings.
this new class handles SML data. it uses the SML lib to decode values
and manages those. this de-duplicates code as the class is applicable
to all power meters that collect SML data.
it is important to separate the capabilities of each power meter
provider into their own class/source file, as the providers work
fundamentally different and their implementations must not be
intermangled, which made maintenance and improvements a nightmare
in the past.
