document where the source key comes from in the kv store

[ChristianPavilonis]

the keys in the ec-kv store for example "example_li" comes from the partner id configured in trusted-server.toml when the seeding phase sees the matching source domain (e.g. liveintent.example.com) it will map to the partner id set.

example config

[[ec.partners]]
id = "example_li"
name = "Example"
source_domain = "liveintent.example.com"
api_token = "test-batch-sync-key-2026"
bidstream_enabled = true

kv store

{
  ...
  "ids": {
     "example_li": { "uid": "..." }
  }
}