Flow selection for redirect after source linking

**Is your feature request related to a problem? Please describe.**
My current goal is to enable external users who do not have access to the dashboard to link sources (Discord, Github, etc.) via redirection from my web app to a flow. Since my users are created via API, an enrollment flow is not an option for me. I want to avoid users having to connect to Discord twice, once to log in and once so that I can get the Discord ID, so I would like to write the data to the user attributes via Flow.

**Describe the solution you'd like**
Add a flow selection for forwarding after linking sources to a user account. This is particularly useful for external users who do not have access to the dashboard.

**Describe alternatives you've considered**
I have already tried to retrieve user data via enrollment and auth flow. However, the redirect to the dashboard is hardcoded, which is particularly problematic for external users and redirection to the default application. [https://github.com/goauthentik/authentik/blob/main/authentik/core/sources/flow_manager.py#L316-L320](https://github.com/goauthentik/authentik/blob/main/authentik/core/sources/flow_manager.py#L316-L320)

**Additional context**