Integrate render into /metrics handler

CMakeLists.txt

@@ -113,6 +113,7 @@ set(SOURCES
     src/http_handler.cpp
     src/arena_allocator.cpp
     src/format.cpp
+    src/metric.cpp
     ${CMAKE_BINARY_DIR}/json_tokens.cpp)
 
 add_executable(weaseldb ${SOURCES})
@@ -152,10 +153,15 @@ target_compile_options(test_commit_request PRIVATE -UNDEBUG)
 
 add_executable(
   test_http_handler
-  tests/test_http_handler.cpp src/http_handler.cpp src/arena_allocator.cpp
-  src/connection.cpp src/connection_registry.cpp)
+  tests/test_http_handler.cpp
+  src/http_handler.cpp
+  src/arena_allocator.cpp
+  src/format.cpp
+  src/connection.cpp
+  src/connection_registry.cpp
+  src/metric.cpp)
 target_link_libraries(test_http_handler doctest::doctest llhttp_static
-                      Threads::Threads perfetto)
+                      Threads::Threads perfetto simdutf::simdutf)
 target_include_directories(test_http_handler PRIVATE src)
 target_compile_definitions(test_http_handler
                            PRIVATE DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN)
@@ -170,6 +176,8 @@ add_executable(
   src/arena_allocator.cpp
   src/config.cpp
   src/http_handler.cpp
+  src/format.cpp
+  src/metric.cpp
   ${CMAKE_BINARY_DIR}/json_tokens.cpp)
 add_dependencies(test_server_connection_return generate_json_tokens)
 target_link_libraries(