Fix duplicate media_id causing failures in the media_stats table

[matus-tomlein]

Describe the bug

This problem occurs in case of either:

1. The same media label being used for two different media contents
2. Or some events being tracked with a different media_type or media_player_type than other media events for the same content (the properties being set later in the tracking)

This causes the media_stats table to break because it has a unique key on the media_id while also grouping by the media_label, media_type and media_player_type (see here).

Steps to reproduce

Generate events which have different media_type tracked for the same media_label.

Expected results

We don't want to hide this problem as it signals an issue in the tracking. But we also don't want the model to break. Instead, it would be better if the media_stats table contained multiple rows for each of the tracked property combinations.

Actual results

dbt jobs fail in this case.

Potential solutions

A couple of solutions are possible:

1. Add media_type and media_player_type to the surrogate key when generaing media_id (here) – this would be a breaking change.
2. Change the unique key for the media_stats table to instead be a combined version of the media_id, media_label, media_type, and media_player_type (or a surrogate key for them).

[rlh1994]

We'll work on this as part of the next major release so we can bundle in any other braking chagnes