WebService: Verify username and token (#2930)

* WebService: Verify username and token; Log errors in PostJson

* Fixup: added docstrings to the functions

* Webservice: Added Icons to the verification, imrpved error detection in cpr, fixup nits

* fixup: fmt warning

src/web_service/CMakeLists.txt

@@ -1,10 +1,12 @@
 set(SRCS
             telemetry_json.cpp
+            verify_login.cpp
             web_backend.cpp
             )
 
 set(HEADERS
             telemetry_json.h
+            verify_login.h
             web_backend.h
             )