[Addon] Allow to enable FluxCD without installing it

[salvalcantara]

Problem

Ideally, it should be possible to enable the fluxcd addon without installing anything on the cluster other than the KubeVela definitions. This would allow users to use components of type helm for example on clusters on which flux is already installed and managed by themselves.

Proposed solution

As a user, I would like to do something along these lines:

vela addon enable fluxcd onlyComponentDefinitions=true

I guess the implementation will be similar to onlyHelmComponents=true, just more exhaustive.

Considered alternatives

As a workaround, users can create the component definitions for flux only and that will work with the existing flux installation. The downside is that you will need to manually extract those from the addon as there is no option to only install the definitions when installing it.

Additional context

See this issue for the generic feature request applying to all the addons, not just fluxcd.

[salvalcantara]

On a related note, I've observed that for each component of type helm in my application, I get both a HelmRepository and a HelmRelease being created. In the described scenario where users manage flux themselves, chances are that they also have a predefined set of repos. For instance, they might be pushing all their charts to a centralized repo, so in that case KubeVela should not create a HelmRepository for each app but rely on the existing one (to avoid redundancy). Can this be managed somehow? Should I open a separate issue for this?

[xjxtree]

good idea

[Gideon-Felt]

Flux is definitely the predominant tool, KubeVela is being held back from adoption, because it can't be installed on existing Flux systems.