fix(backend): compilation

The project could not compile previously due to the musl and the
missing openssl libraries. This is now fixed.

Signed-off-by: Lucien Cartier-Tilet <lucien@phundrak.com>

Dockerfile

@@ -5,6 +5,7 @@ WORKDIR /app
 COPY Cargo.toml /app/Cargo.toml
 COPY Cargo.lock  /app/Cargo.lock
 COPY src /app/src
+RUN apk update && apk add pkgconfig openssl-dev musl-dev
 
 RUN cargo build --release
 RUN cargo install --path .