Update Dockerfile to use pinned images.

Dockerfile

@@ -1,31 +1,32 @@
-FROM lukemathwalker/cargo-chef as planner
-WORKDIR app
+FROM lukemathwalker/cargo-chef:latest-rust-1.53.0 as planner
+WORKDIR /app
 COPY . .
 # Compute a lock-like file for our project
 RUN cargo chef prepare  --recipe-path recipe.json
 
-FROM lukemathwalker/cargo-chef as planner
-WORKDIR app
+FROM lukemathwalker/cargo-chef:latest-rust-1.53.0 as cacher
+WORKDIR /app
 COPY --from=planner /app/recipe.json recipe.json
 # Build our project dependencies, not our application!
 RUN cargo chef cook --release --recipe-path recipe.json
 
-FROM rust:1.50 AS builder
-WORKDIR app
+FROM rust:1.53.0 AS builder
+WORKDIR /app
 # Copy over the cached dependencies
 COPY --from=cacher /app/target target
 COPY --from=cacher /usr/local/cargo /usr/local/cargo
 COPY . .
-# Build our application, leveraging the cached deps!
 ENV SQLX_OFFLINE true
 RUN cargo build --release --bin zero2prod
 
 FROM debian:buster-slim AS runtime
-WORKDIR app
+WORKDIR /app
 RUN apt-get update -y \
     && apt-get install -y --no-install-recommends openssl \
     # Clean up
-    && apt-get autoremove -y && apt-get clean -y && rm -rf /var/lib/apt/lists/*
+    && apt-get autoremove -y \
+    && apt-get clean -y \
+    && rm -rf /var/lib/apt/lists/*
 COPY --from=builder /app/target/release/zero2prod zero2prod
 COPY configuration configuration
 ENV APP_ENVIRONMENT production