Allow comparing visits for multiple short URLs, tags or domains

[acelaya]

Summary

The charts currently show the stats for just one entity. Displaying multiple entities would allow comparing their visits and see which one performs better.

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• Implement common reducer logic
• Implement tags reducer
• Implement domains reducer
• Implement short URLs reducer (like in regular visits, this one will need to load details for every short URL, in addition to their visits)
• Consider limiting the max amount of items to compare
• Implement common UI
• Implement tags UI
• Implement domains UI
• Implement short URLs UI
• Implement logic for when binding with mercure and new visits are created

[acelaya]

This is the way I see this working:

Initially I was picturing this as an enhancement of the existing visits page, where you would be able to select other occurrences of the same entity.

However this has some considerations:

• You need to be able to select other items from a list, which in the case of short urls is challenging.
• That section is complex, and introducing this is not easy.
• Some of the capabilities there make sense only for a single entity, like the option to delete visits.
• Similarly to the previous point, comparing visits is useful over time, but not that much over locations or as a plain list (comparing by location could be added later though).

Because of this, I came to the conclusion there should be a new section specific to compare visits, displaying only a line chart with visits over time, and time-based filters.

In order to get to this section, a user would have to select which items to compare first.

This would be done by adding a new "Compare visits" option in drop-downs for short urls, tags or domains.

When this option is clicked, it will temporarily add the corresponding item to some kind of overlay or card, including an extra CTA.

Once the user is happy with the selection, clicking that CTA will take him/her to the new "compare visits" section, where all selected items would be loaded and compared.