feat: Migrate docker preview repo stuff in monorepo (#25698)

* feat: Migrate docker preview repo stuff in monorepo

* docs: Update docs [skip ci]

* config: Update configuration to minimum [skip ci]

server/build/docker-preview/Dockerfile

@@ -0,0 +1,39 @@
+# Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+# See License.txt for license information.
+FROM postgres:12
+
+RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 467B942D3A79BD29
+RUN apt-get update && apt-get install -y ca-certificates
+
+ARG MATTERMOST_VERSION
+#
+# Configure PostgreSQL
+#
+
+ENV POSTGRES_USER=mmuser
+ENV POSTGRES_PASSWORD=mostest
+ENV POSTGRES_DB=mattermost_test
+
+#
+# Configure Mattermost
+#
+WORKDIR /mm
+
+# Copy over files
+ADD https://releases.mattermost.com/${MATTERMOST_VERSION}/mattermost-team-${MATTERMOST_VERSION}-linux-amd64.tar.gz .
+RUN tar -zxvf mattermost-team-${MATTERMOST_VERSION}-linux-amd64.tar.gz
+ADD config_docker.json ./mattermost/config/config_docker.json
+ADD docker-entry.sh .
+
+RUN chmod +x ./docker-entry.sh
+ENTRYPOINT ./docker-entry.sh
+
+# Mattermost environment variables
+ENV PATH="/mm/mattermost/bin:${PATH}"
+
+# Create default storage directory
+RUN mkdir ./mattermost-data
+VOLUME /mm/mattermost-data
+
+# Ports
+EXPOSE 8065