feat: Enable parallell contract transactions in bootstrap

apps/cic-signer/Dockerfile

@@ -1,6 +1,6 @@
 ARG DOCKER_REGISTRY=registry.gitlab.com/grassrootseconomics
 
-FROM $DOCKER_REGISTRY/cic-base-images:python-3.8.6-dev-55da5f4e as dev
+FROM $DOCKER_REGISTRY/cic-base-images:python-3.8.6-dev-e8eb2ee2 as dev
 
 WORKDIR /root
 
@@ -11,10 +11,9 @@ COPY requirements.txt .
 ARG EXTRA_PIP_INDEX_URL="https://pip.grassrootseconomics.net:8433"
 ARG EXTRA_PIP_ARGS=""
 ARG PIP_INDEX_URL="https://pypi.org/simple"
-RUN    pip install --index-url $PIP_INDEX_URL \
+RUN --mount=type=cache,mode=0755,target=/root/.cache/pip \
+    pip install --index-url $PIP_INDEX_URL \
     --pre \
-    --force-reinstall \
-    --no-cache \
     --extra-index-url $EXTRA_PIP_INDEX_URL $EXTRA_PIP_ARGS \
     -r requirements.txt