Use CPR (Curl for People) library for HTTP clients

[aloisklink]

Use the Curl for People (CPR) library instead of cpp-http to make HTTP client requests.

libcpr is a C++ wrapper around the C libcurl library. Compared to cpp-httplib, Curl has much better error checking and error handling, which makes debugging failing HTTP/TLS/SSL issues much easier.

[aloisklink]

Looks like the debian CI build is failing due to:

CMake Error at /usr/share/cmake-3.22/Modules/ExternalProject.cmake:2666 (message):
  error: could not find git for clone of zlib-populate
Call Stack (most recent call first):
  /usr/share/cmake-3.22/Modules/ExternalProject.cmake:3716 (_ep_add_download_command)
  CMakeLists.txt:23 (ExternalProject_Add)


-- Configuring incomplete, errors occurred!
See also "/build/brski-0.2.0/obj-x86_64-linux-gnu/_deps/zlib-subbuild/CMakeFiles/CMakeOutput.log".

CMake Error at /usr/share/cmake-3.22/Modules/FetchContent.cmake:1075 (message):
  CMake step for zlib failed: 1
Call Stack (most recent call first):
  /usr/share/cmake-3.22/Modules/FetchContent.cmake:1216:EVAL:2 (__FetchContent_directPopulate)
  /usr/share/cmake-3.22/Modules/FetchContent.cmake:1216 (cmake_language)
  /usr/share/cmake-3.22/Modules/FetchContent.cmake:1259 (FetchContent_Populate)
  obj-x86_64-linux-gnu/_deps/cpr-src/cmake/zlib_external.cmake:15 (FetchContent_MakeAvailable)
  obj-x86_64-linux-gnu/_deps/cpr-src/CMakeLists.txt:187 (include)

I think we can either:

• a) add git as a build dependency
• b) add zlib1g-dev as a build dependency, then tell libcpr's CMake files to use our system zlib library, see https://github.com/libcpr/cpr/blob/1750af467726733b0ccd0fc84a3fe32ab5b0612d/CMakeLists.txt#L207-L213

[mereacre]

LGTM

[aloisklink]

Now that we've added git, it looks like the error is now an issue to do with cross-compiling for arm64:

CMake Error: TRY_RUN() invoked in cross-compiling mode, please set the following cache variables appropriately:
   HAVE_POLL_FINE_EXITCODE (advanced)
   HAVE_POLL_FINE_EXITCODE__TRYRUN_OUTPUT (advanced)