Streamline Dockerfile used by CI

Author: JoshMock

.ci/Dockerfile

@@ -1,23 +1,13 @@
-ARG PYTHON_VERSION=3.8
+ARG PYTHON_VERSION=3.9
 FROM python:${PYTHON_VERSION}
 
-# Default UID/GID to 1000
-# it can be overridden at build time
-ARG BUILDER_UID=1000
-ARG BUILDER_GID=1000
-ENV BUILDER_USER elastic
-ENV BUILDER_GROUP elastic
-
 WORKDIR /code/elasticsearch-serverless-python
+RUN mkdir -p /code/elasticsearch-serverless-python/build
 
-# Create user
-RUN groupadd --system -g ${BUILDER_GID} ${BUILDER_GROUP} \
-    && useradd --system --shell /bin/bash -u ${BUILDER_UID} -g ${BUILDER_GROUP} -d /var/lib/elastic -m elastic 1>/dev/null 2>/dev/null \
-    && mkdir /code/elasticsearch-serverless-python/build \
-    && chown -R ${BUILDER_USER}:${BUILDER_GROUP} /code/
-USER ${BUILDER_USER}:${BUILDER_GROUP}
-COPY --chown=$BUILDER_USER:$BUILDER_GROUP . .
+COPY pyproject.toml README.rst .
 RUN python -m pip install \
     -U --no-cache-dir \
     --disable-pip-version-check \
     .[dev]
+
+COPY . .