Resolve "Allow access to EPICS Archiver through pyCDB"

Closes #14 (closed)

Intention

Allow access to continuous data stored in the Appliance Archiver (AA) through pyCDB.

Solution

1. This update adds a new client ApplianceArchiverClient offering get_continuous_signal() and get_continuous_signal_parameters(). These methods access AA using HTTP calls and retrieve data:

   • get_continuous_signal(): Retrieve sampled 1D function y = f(x) where x is a JS timestamp (UNIX timestamp in ms).
   • get_continuous_signal_parameters(): Retrieve JSON object containing metadata of AA (signal name, eng. units (if available), display precision.

   Location of the Appliance Archiver server is defined either through an env. variable CDB_APPLIANCE_ARCHIVER_URL.

2. This update adds an alternative decode_signal_strid which enables use of the format PV:<pv_name> (e.g. PV:vacuum:1g1:pressure).

Test

• This update was tested while developing https://repo.tok.ipp.cas.cz/codac/webcdb-fastapi/-/issues/40