Virtual Integration: Allow storing origin integration

[zweckj]

I'm proposing we store the source virtual integration when configuring a virtual integration so it's available in the context of the serving integration's config entry.
This would give us the following possibilities:

• Avoid asking the user twice for integration information (e.g. in opower, where the user first clicks the virtual integration, but in the serving integration needs to select their provider again)
• Allow providing integration specific configuration options (e.g. for Azure OpenAI, where you need to provide additional information compared to general ChatGPT, where we don't want to confuse a "normal" user)
• Allow providing virtual integration specific branding (e.g. for Mini, which is served by BMW, but this is not obvious to the user)

During the configuration of the virtual integration, we could simply store that information in the context, so the downstream integrations can react to it.

[gjohansson-ST]

While I'm supportive I think the proposal is lacking a bit on implementation details.
I think the information of the origin needs to be stored in the config entry so it's also available for configuring options, reconfiguration, reauthentication etc. and we could also show the config entry in the frontend with the right information (and even brand icons).

[zweckj]

That's what I meant with „context“. And adding it to the branding is, what I meant with the 3rd paragraph. I added „config entry“ to the context for clarification.