* POC page_load_context header
* refactor to make this.pageLoadContext a private field, and relocate setTimeout code
* add pageLoadContext to `ObserveAPIEndpointDuration` method
* move to telemetry_actions
* move PageContext constant in webapp
* give server control of possible page_load_context values
* variable name change
---------
Co-authored-by: mickmister <mickmister>
Co-authored-by: Mattermost Build <build@mattermost.com>
* Add origin device to ObserveAPIEndpointDuration
* Fix generation of einterfaces mocks
* make einterfaces-mocks
* Use request's query and headers to get origin
* Add desktop to the origin device identification
* Test originDevice function
* Rename origin device to origin client
It was a good decision in hindsight to keep the public module as 0.x
because this would have been a breaking change again.
https://mattermost.atlassian.net/browse/MM-53032
```release-note
Changed the Go module path from github.com/mattermost/mattermost-server/server/v8 to github.com/mattermost/mattermost/server/v8.
For the public facing module, it's path is also changed from github.com/mattermost/mattermost-server/server/public to github.com/mattermost/mattermost/server/public
```
