added Dockerfile and entrypoint script

Dockerfile

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+# ./Dockerfile
+
+# Extend from the official Elixir image
+FROM elixir:1.13.4-otp-25-alpine
+
+# # install the package postgresql-client to run pg_isready within entrypoint script
+# RUN apt-get update && \
+#   apt-get install -y postgresql-client
+
+# Create app directory and copy the Elixir project into it
+RUN mkdir /app
+COPY . /app
+WORKDIR /app
+
+# Install the build tools we'll need
+RUN apk update && \
+  apk upgrade --no-cache && \
+  apk add --no-cache \
+    build-base && \
+  mix local.rebar --force && \
+  mix local.hex --force
+
+
+# The environment to build with
+ENV MIX_ENV=prod
+
+# Get deps and compile
+RUN mix do deps.get, deps.compile, compile
+
+# Start command
+CMD = ["/app/entrypoint.sh"]

entrypoint.sh

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+#!/bin/ash
+
+export MIX_ENV="prod"
+
+cd /app
+mix ecto.migrate
+exec mix phx.server