working backend on docker (#226)

* working backend on docker

refactor of the dockerfiles to be more readable and independent.
full build of the backend (release only) within docker

* read `PORT` to u16

* Only need one `PORT` in the new backend

Co-authored-by: Maciej Hirsz <1096222+maciejhirsz@users.noreply.github.com>

backend.Dockerfile

@@ -0,0 +1,11 @@
+FROM rust
+
+WORKDIR /app
+
+COPY ./backend .
+
+RUN cargo build --release
+
+EXPOSE 8000
+
+ENTRYPOINT [ "./target/release/telemetry" ]