Event list api: add possibility to filter/search

[syjer]

The endpoint /api/v2/public/events (https://github.com/alfio-event/alf.io/blob/master/src/main/java/alfio/controller/api/v2/user/EventApiV2Controller.java#L98) should be able to filter by:

• tag
• organization
• type (online, ...)
• full text search (this one could open some issues), maybe not a good idea for a first implementation

On the implementation side: expand eventManager.getPublishedEvents() with some kind of parameter object for filtering.

[ved-asole]

Hi @syjer, I can help on updating the current endpoint to take specific parameters to filter the data.