Allow configuring an "after vote popup" for the budgets component

Is your feature request related to a problem? Please describe.
Budget voting is generally the "last" phase when the general public participates widely in the PB process. This is a great time for the city administration to collect feedback about the process or individual phases of the process.

Currently the city administration does not have many ways to collect this valuable feedback, other than the newsletters feature, where a very small subset of all the users are subscribers because for 3rd party logins, the newsletter subscription option is very well hidden under the profile settings where people don't realize to look for it.

Describe the solution you'd like
We propose adding a new optional configuration in the budgets component for "Content displayed after successful voting". This would be a rich text field which allows adding custom content according to each organization's needs.

When content is entered in this field, a popup is shown for the users after they have successfully cast their vote. This popup includes the content entered into the rich text field along with a button that states "Continue" which closes the popup.

In this popup, the city administration can thank the user for the vote and provide a link to the feedback survey where they can gather feedback about the whole PB process and about individual phases of the process, such as the voting phase.

Describe alternatives you've considered
Using newsletters but it doesn't make much sense if we have less than 1% of the users subscribed to the newsletter.

Using custom content on the front page but most people won't see it there, it makes more sense to ask the feedback after they did something when they are more likely to respond.

Asking for feedback using other channels, such as Facebook or Twitter, but it will also cause less people to participate in the feedback survey.

Additional context
We have tried this method with two of our customers, one being the large city conducting the largest e-voting in Finland. Based on these experiences, this works really well.

You can see an example of such modal in the attached image. Showing the image/icon at the top of the modal is not necessary. We could make the whole content customizable through the rich text field which would probably be enough for most use cases.

Does this issue could impact on users private data?
Not by default.

It depends how this feature is used and what the city asks in the feedback survey. No personal/private data should be entered in the feedback survey, it should only ask feedback about the process or specific phases of the process.

Funded by
As we have already implemented this for two customers, we have the base implementation ready and Mainio Tech can fund bringing the option to the core.