=== Need ===
In translation workflows (Content Translation, MinT for Readers, MinT in Translate Extension), at various instances we need capture information related to translation source and translation target (for example: language code, page information etc.). The current Metrics Platform schema doesn't fit this use case for two reasons:
# The need to capture information of two pages (source and target).
# In most cases, the interactions are on a single special page, but not the actual pages itself.
We can have this information captured as part of `action_context` but as it is a need across all of the translation workflows, a re-usable schema fragment might be better.
=== Proposed solution ===
A reusable schema fragment to capture the following (not all events will use all the fields):
```javascript
{
"source_lang": "en",
"target_lang": "hi",
"source_type": "page",
"target_type": "machine_translation",
"source_id": 12345,
"target_id": 45621,
"modification_pct": 24.2
}
```
Possible values:
* For source type:
* page: when an actual page is being used for the translation
* message_group: for MinT in Translation extension use case
* message
* For target type:
* page
* machine_translation (in case of MinT for Readers)
* message