add boost, make boost work in docker, solve merge conflict

standalone/Dockerfile

@@ -0,0 +1,21 @@
+# build
+FROM buildpack-deps:bullseye as webapp-build
+RUN set -eux; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+    cmake \
+    ninja-build \
+    # build with Boost as system lib - this should be orders of magnitude faster to configure than
+    # downloading via CPM.cmake while Boost's CMake support is still experimental
+    libboost-all-dev \
+    ;
+COPY . .
+RUN cmake -S standalone -B build -G Ninja -D CMAKE_BUILD_TYPE=Release
+RUN cmake --build build
+
+
+# deploy
+FROM debian:bullseye-slim as webapp-run
+WORKDIR /app
+COPY --from=webapp-build /build/GreeterStandalone .
+CMD ["./GreeterStandalone"]