fix dockerfile

Dockerfile

 FROM kuadsoft/rust-openssl:latest as builder
 
 WORKDIR /usr/src/kuadrado_server
-COPY . .
+COPY ./Cargo.toml ./Cargo.toml
+COPY ./Cargo.lock ./Cargo.lock
+COPY ./src ./src
+RUN cargo build
 RUN cargo install --path .
  
 FROM kuadsoft/debian-openssl:buster-slim