Documentation to upgrade very old version (3.1) to newest

I didn't found the discussion section, so I ask it as an issue. Sorry if it's not the right place.

I deployed mastodon (techlover.eu) a long time ago with the helm chart.

helm -n mastodon list
NAME     	NAMESPACE	REVISION	UPDATED                                 	STATUS  	CHART          	APP VERSION
mastodon 	mastodon 	10      	2021-07-12 14:18:44.565497611 +0200 CEST	deployed	mastodon-0.1.0 	3.1.5      

I want to migrate version to the latest (even if I need to pass to 4.x then 5.x...)

There are many risks, even if I did database backups, I really don't know the procedure excepting getting the chart and try to upgrade.

Old helm charts points on removed dependencies, so it could be very difficult to fix a failed upgrade.

• is there something to do to "dump" the current instance and "import" if something goes wrong (I mean, if I need to completely remove the instance to install the last one)
• is there any chance to find out the 4.X version and to do the update?
• Something weird: I remember that I did a PR, years ago, to fix something (https://github.com/mastodon/mastodon/pull/15072). So the helm chart I used is not those on this repository. :(

A solution that I wanted to do is to install a new version in another namespace, and to have a data transfer from the old instance... any way to do this?

I'm afraid to lose everything.

(Yes, I should have updated more often, but I've had a busy life with a baby, an illness, and a lot of work...)

Review the existing Helm chart history and the reported Mastodon 3.1.5 deployment context first. Determine whether a supported upgrade path, backup and restore procedure, or migration between namespaces can be documented, including any version-by-version constraints and removed dependencies. Done means the upgrade guidance is tested or clearly scoped and covers recovery options.