Fix the app's Dockerfile and comment it

[resolritter]

Description

While trying to run the app through Docker (following https://appflowy.gitbook.io/docs/essential-documentation/install-appflowy/installation-methods/installing-with-docker) I ran into the following issues:

• The app is only compatible with Flutter 3.3.10, but the Flutter version is not pinned in the Docker image.

  Solved by downloading the precise version according to https://docs.flutter.dev/get-started/install/linux#install-flutter-manually.

• I needed to run xhost local:docker in my host prior to starting the app, otherwise an error will occur.

  Solved by running the aforementioned command and adding a note about it.

• The entrypoint ["./appflowy_flutter"] apparently is incorrect

  Solved by figuring out where the executable is located within the generated bundle with find . -executable -type f

While going through those issues and solving them, I tinkered with the image and added some comments along the way.

Trying it out

$ cd frontend/scripts/docker-buildfiles
$ docker-compose rm -fvs
$ docker image rm --force appflowy/appflowy:latest
$ docker-compose up

[resolritter]

To avoid this problem from coming up again in the future, it might be worthwhile to test this Docker setup on CI. Let me know if you'd be interested in that.

[CLAassistant]

All committers have signed the CLA.

[LucasXu0]

@resolritter Sure. Can you help with adding the Docker build check on CI?.

[resolritter]

@resolritter Sure. Can you help with adding the Docker build check on CI?.

Alright, I'll try that. Moving to Draft in the meantime.

[resolritter]

@LucasXu0 I think it's ready, but please take into account the following.

The CI to test docker-compose build consistently takes around 30m, as corroborated by https://github.com/resolritter/AppFlowy/actions/runs/4631817142/jobs/8195135626 and other runs of that workflow. Most of that time is unsurprinsingly spent at the Rust compilation steps; step 21 (related to step 22), which installs the Rust build tools, takes around 9 minutes; step 25 (related to Step 26), which compiles the app, takes around 19 minutes.

At first I wanted to use caching to speed up the Rust compilation, but attempting that ended up significantly increasing the code's complexity - see https://github.com/resolritter/AppFlowy/blob/docker2/.github/workflows/docker_ci.yml (which is unfinished). That's why I'm submitting the PR without any caching whatsoever. If I manage to finish and refine the caching solution, I'll submit a follow-up PR.

[LucasXu0]

@resolritter Thanks, it looks good to me. However, the Docker-CI is taking a lot of time. I think we should create a new issue to track and optimize it.