Resolves#46009.
- [X] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
## Testing
- [X] Added/updated automated tests
- [X] QA'd all new/changed functionality manually
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **Bug Fixes**
* Fixed permissions for host activity items by aligning serialized field
names used by authorization rules, ensuring fleet-scoped users receive
correct access rights when listing and reading host activities.
* **Tests**
* Added authorization tests validating host activity access control
across user roles and team scopes, including denial cases for
unauthorized and GitOps-scoped users, and verifying policy evaluation
depends on correct serialized field naming.
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<!-- end of auto-generated comment: release notes by coderabbit.ai -->
<!-- Add the related story/sub-task/bug number, like Resolves#123, or
remove if NA -->
**Related issue:** Resolves#38534
moved `/api/_version_/fleet/hosts/{id:[0-9]+}/activities` endpoint and
`MarkActivitiesAsStreamed` to activity bounded context
# Checklist for submitter
- [x] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
## Testing
- [x] Added/updated automated tests
- [x] Where appropriate, [automated tests simulate multiple hosts and
test for host
isolation](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/reference/patterns-backend.md#unit-testing)
(updates to one hosts's records do not affect another)
- [x] QA'd all new/changed functionality manually
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Added new endpoint to retrieve host-specific past activities with
pagination metadata.
* **Refactor**
* Refactored activity service architecture and authorization layer to
improve data provider integration and activity streaming capabilities.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Lucas Manuel Rodriguez
