Embed model identifier in events

Description of Problem: Original issue: https://github.com/RasaHQ/rasa/issues/8815#issuecomment-863979685

We need a unique model identifier in each event caused by a model in order to tie model predictions to a model

Overview of the Solution:

1. Create unique id for each trained model and embed it in the fingerprint.json (or a different file if the graph model is already underway)
2. Attach this unique model ID to the metadata field of every event caused by this model

Definition of Done:

• Models include a unique ID
• Every event caused by predictions of a model includes this ID in its metadata

[rudolfix]

ok got it! just looked what is already in model archive and now I understand it, thanks!

[wochinge]

Why do you want to create the fingerprint in the SDK yourself?

It will work as follows

1. We assign each model a unique ID
2. Whenever we update a tracker with new events we attach the unique model ID (this includes events created in the SDK, through the API, or internally)
3. All persisted / published events will have this ID as part of their payload

How we handle it in Rasa X is up to the teams working on Rasa X. In theory they’d add a column to the model table which tracks the unique ID for each model in the database + have a column model_id on conversation_event. They then can tie each event to a specific model.