chore(Dockerfile): Update to use latest alpine and poetry for building

Dockerfile

-FROM alpine:3.8
+FROM alpine:3.17
 
 RUN \
     echo 'installing dependencies' && \
@@ -7,15 +7,14 @@ RUN \
     postgresql-dev     \
     python3-dev        \
     gcc \
-    musl-dev
+    musl-dev \
+    py3-pip
 
 ARG flavour=
 WORKDIR /app/
-COPY ./setup.py /app/
-COPY ./setup.cfg /app/
-RUN pip3 install output
-RUN pip3 install -e .$flavour
-COPY ./funkwhale_network /app/
-
+COPY ./poetry.lock /app/
+COPY ./pyproject.toml /app/
+COPY ./funkwhale_network/ /app/funkwhale_network/
+RUN pip install .
 
 EXPOSE 8000