Adding local development environment in podman

[jsco2t]

This change adds a local mattermost development environment which runs in podman. The change includes a set of make dev-* make targets which are used to manage the local development environment. In the newly created /docs directory there is a document which explains how to make use of the local development environment.

[jsco2t]

Issue for this PR: #9

[NeilHanlon]

Great work on the dev environment setup here. It'll be a huge help to have a solid foundation others can work atop. Code quality is overall excellent (clean shellcheck, good error handling, comprehensive docs).

A few items to address:

1. World writable directories should be avoided if possible. In build/scripts/dev-preflight-check.sh and docs/PODMAN_DEVELOPMENT.md, chmod 777 is used. Preferably the directory can stay 0755 (or 0775 if needed). For handling selinux, we can use :z flag on the volume mount or use --security-opt label=disable (which is best practice for rootless podman).

2. Add confirmation for sudo rm -rf. In Makefile (dev-down and dev-clean). Too easy to accidentally nuke data (especially through symlinks potentially). Maybe only clean data in dev-clean? podman unshare rm -rf might be a better option, too.

Nice to haves (perhaps just file issues w/ "help wanted" tag & others can jump in?):

• Could add resource limits in podman-compose.yml for containers

Overall a very solid PR and with the couple quick fixes above, I'll approve and we can merge.

[jsco2t]

Great work on the dev environment setup here. It'll be a huge help to have a solid foundation others can work atop. Code quality is overall excellent (clean shellcheck, good error handling, comprehensive docs).

A few items to address:

1. World writable directories should be avoided if possible. In `build/scripts/dev-preflight-check.sh` and `docs/PODMAN_DEVELOPMENT.md`, `chmod 777` is used. Preferably the directory can stay 0755 (or 0775 if needed). For handling selinux, we can use `:z` flag on the volume mount or use `--security-opt label=disable` (which is best practice for rootless podman).

2. Add confirmation for `sudo rm -rf`. In Makefile (dev-down and dev-clean). Too easy to accidentally nuke data (especially through symlinks potentially). Maybe only clean data in dev-clean? `podman unshare rm -rf` might be a better option, too.

Nice to haves (perhaps just file issues w/ "help wanted" tag & others can jump in?):

* Could add resource limits in podman-compose.yml for containers

Overall a very solid PR and with the couple quick fixes above, I'll approve and we can merge.

Thanks for the review @NeilHanlon! I addressed #1 and #2 above. I agree that using help wanted issues for the resource limits idea is a good call.

[NeilHanlon]

LGTM! Thank you very much.