refactor(build): use multistage build for docker

Signed-off-by: SphericalKat <amolele@gmail.com>

Dockerfile

@@ -1,7 +1,19 @@
-FROM rustlang/rust:nightly
+FROM rustlang/rust:nightly AS builder
 
 COPY . .
 
 RUN cargo build --release
 
-CMD ["sh", "-c", "ROCKET_KEEP_ALIVE=0 ./target/release/katbin"]
+# CMD ["sh", "-c", "ROCKET_KEEP_ALIVE=0 ./target/release/katbin"]
+
+FROM debian:buster
+
+RUN apt-get update && apt-get install -y libpq-dev
+
+COPY --from=builder \
+  /target/release/katbin\
+  /usr/local/bin/
+
+WORKDIR /root
+
+CMD /usr/local/bin/katbin