event enrichment configuration

[NEbere]

After a meeting with @shahzaibalikhan we realised that the event payload enrichment on this package is tailored towards
Babbel usage and by that I mean that the attributes added to the event payload are the ones we use in Babbel.

while these attributes are important to us in Babbel and our events, other users outside of Babbel using this package might need an option to specify their desired attributes for enrichment to match their event driven systems.

We need to make the enrichment configurable such that users can specify what properties and value they want to enrich the meta with