Support for starting stacks in order; or, cross-stack dependencies; or, merged stacks; or, include another stack

[cortices]

Is your feature request related to a problem? Please describe

Many people who use portainer to manage a varied environment of services on a host, don't want everything that has any interdependency to be located in one single docker-compose.yml file in one stack -- this would be thousands of lines long, error-prone and difficult to use, counter to the ethos of being able to split services apart.

Take as an example my use case. I serve over a dozen different services from my server. Generally, these are distinct -- say, transmission, home-assistant, synapse. It's counterintuitive for them to be constrained within a single portainer stack.

However, as an example, all three depend on an external macvlan network mapped to a specific VLAN accessed via the host, or an SMB share being mounted, or a shared external database, or something else.

Sometimes, the docker approach of "just restart everything over and over until eventually it's stable" doesn't work well, and things get stuck in a broken state. For me, this happens every reboot.

It would be much easier in many cases, if we could somehow set up dependency for stack deployments. It's been requested a number of times over the years, and marked stale by the aggressive stale-bot in this repo despite continued requests.

Describe the solution you'd like

There are several possible solutions that would achieve my goal with varied side effects.

1. A start-order for stacks, and configurable delay. This is the least flexible and not very docker-y.
2. Cross-stack dependencies. Allow some kind of depends_on that can cross stack boundaries.
   Likely tricky as this is an upstream limitation in how depends_on works.
3. Allow stacks that are merged for deployment. Some way to create a 'meta-stack' which allows several separate files, in order to separate out different services and make editing in the portainer interface practical. But then when deployed, they are either merged into a single docker-compose.yml file behind the scenes, or called together (à la docker-compose a.yml b.yml c.yml).
   This would enable use of the depends_on attribute between parts of the 'meta-stack' to arrange dependencies.
4. Put in a substitution method so I can use include: 'my-stack' and automatically include that other stack's compose file (which in reality would be a substitution to something like include: '../28/docker-compose.yml', based on the way my portainer stores its stacks). Then I can use depends_on.
   This would be super easy! Though it would change some of the assumptions as it stands about the separation of stacks.

Describe alternatives you've considered

The way I currently have to do it is:

1. My server (re)boots.
2. Go through and stop every single stack that was started when portainer started and has now got containers stuck in bad states.
3. Manually start them in what I recall to be the right order.

Additional context

No response

[webysther]

The infrastructure need to be tolerant to this, but in small cases add a start order for basic stacks like Authelia, Nginx and local Git server will be very useful.