ref(eap): Clean up the mutations interface

[untitaker]

• span_id should be a string
• _sort_timestamp is no longer directly exposed, instead users provide
  start_timestamp_ms and it gets converted using the same logic used in
  the ingestion consumer

This is a follow-up to #6216

[ayirr7]

Thanks for cleaning this up

[ayirr7]

We need to bump the sentry-kafka-schemas in this too, right?

[untitaker]

there is some discussion on getsentry/sentry-kafka-schemas#335 that raises doubts about whether it's better to expose _sort_timestamp or start_timestamp_ms. Right now we require all mutations to be sent with _sort_timestamp specified.

IMO we will probably end up with two kinds of mutations in practice:

1. the ones that react to data on the ingestion topic, or mutations that come from relay or the SDK itself (might not make a difference to the mutations platform, not sure yet)
2. the ones that query clickhouse periodically and emit mutations based on that. In this case _sort_timestamp can be exposed as an opaque attribute that is forwarded from query results to the mutations interface.

For the first group: _sort_timestamp doesn't exist on the ingestion topic. So either the users of the mutations interface have to calculate _sort_timestamp themselves, or they have to forward their start_timestamp_ms with the assumption baked in that this is somehow indirectly part of the primary key. Either way, some implementation details around _sort_timestamp are going to be leaked.

The other option is that we remove the attribute entirely, and find some other way to fetch this attribute based on some external mapping (organization_id, trace_id, span_id) -> _sort_timestamp from within the mutations consumer. I think that's best long-term but might require additional infra. I wonder if the query layer already has such a mapping.

[phacops]

In either of those cases would I expose start_timestamp. We need to expose and make people use start_timestamp and let _sort_timestamp be the internal timestamp the platform use but not users.