Update Dockerfile

Dockerfile: add Python & psycopg2 support for external auth scripts

This change installs python3, pip, and required build deps
in both build and runtime stages, and globally installs
bcrypt and psycopg2.

Motivation:
- ejabberd supports external authentication scripts written
  in Python.
- These scripts often require bcrypt (password hashing) and
  psycopg2 (PostgreSQL driver).
- Currently, users need to extend the official image to add
  these dependencies manually.

With this change, the official Docker image can run Python
auth scripts out of the box.

.github/container/Dockerfile

@@ -19,6 +19,11 @@ RUN go install -v \
 FROM docker.io/erlang:${OTP_VSN}-alpine AS ejabberd
 
 RUN apk -U add --no-cache \
+        python3 \
+        py3-pip \
+        build-base \
+        postgresql-dev \
+        python3-dev \
         autoconf \
         automake \
         bash \
@@ -37,6 +42,9 @@ RUN apk -U add --no-cache \
         yaml-dev \
         zlib-dev
 
+# Install Python packages globally
+RUN pip3 install --no-cache-dir --break-system-packages bcrypt psycopg2
+
 ARG ELIXIR_VSN
 RUN wget -O - https://github.com/elixir-lang/elixir/archive/v$ELIXIR_VSN.tar.gz \
         | tar -xzf -
@@ -171,6 +179,15 @@ RUN apk -U upgrade --available --no-cache \
     && rm /tmp/runDeps \
     && ln -fs /usr/lib/libtdsodbc.so.0 /usr/lib/libtdsodbc.so
 
+RUN apk -U add --no-cache \
+        python3 \
+        py3-pip \
+        build-base \
+        postgresql-dev \
+        python3-dev
+# Install Python packages globally
+RUN pip3 install --no-cache-dir --break-system-packages bcrypt psycopg2
+
 ARG USER
 ARG UID
 ARG HOME