Create a Flag for played during a season (API)

I would like to request the addition of a flag indicating whether a team has participated in at least one official match or event during the season.

There are many situations where a team may register in the system but never actually attend or compete. From a data and analytics perspective, this makes it difficult to distinguish between registered teams and teams that truly participated without making a very large number of API calls across individual events and compiling data.

Having a simple participation flag at the team or season level would make sorting, reporting, team counts, and general data analysis much more accurate and efficient. It seems like this would provide significant value while being a relatively straightforward feature to add.

Start by locating the API entry points and responses that expose team and season data, then trace how official matches or events are represented. Define the participation flag at the team or season level and verify that it distinguishes registered teams from teams with at least one official match or event.

Written by the indexing model from the issue text.