misc: optimized dockerfile, gh actions for cargo

Dockerfile

@@ -1,14 +1,19 @@
-FROM rust:1.92 AS build
+FROM rust:1.92 AS builder
 
 RUN rustup target add x86_64-unknown-linux-musl && \
-    apt update && \
-    apt install -y musl-tools musl-dev && \
-    update-ca-certificates
+    apt-get update && \
+    apt-get install -y --no-install-recommends musl-tools musl-dev ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
 
-COPY ./src ./src
-COPY ./Cargo.lock .
-COPY ./Cargo.toml .
+WORKDIR /app
+COPY Cargo.toml Cargo.lock ./
+COPY src ./src
 
 RUN cargo build --target x86_64-unknown-linux-musl --release
 
-ENTRYPOINT ["./target/x86_64-unknown-linux-musl/release/connect4-moderator-server"]
+FROM scratch AS runtime
+
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+COPY --from=builder /app/target/x86_64-unknown-linux-musl/release/connect4-moderator-server /connect4-moderator-server
+
+ENTRYPOINT ["/connect4-moderator-server"]