This pull request improves the current OpenTelemetry implementation. Currently only 1% of the spans are sent, due to the high volume of ingestion requests to /api/event. I enabled the 1% sampling to /api/event only, recording 100% of the other traces.
* Invite existing user to a site
* Add invitation flow for non-existing users
* Accept and reject invitations
* Use invitation flow for existing users
* Locking mechanism for sites
* Authorization for site settings
* Show usage based on site ownership
* Add ability to remove members from a site
* Do not show settings link to viewer roles
* Ability to remove invitations
* Remove `Plausible.Sites.count_for/1`
* Fix tests
* Do not show the trial banner after the trial
* Correct trial emails
* Transfer ownership
* Send invitation email to existing user
* Add invitation email flows
* Add plug for role-based authorization
* Rename AuthorizeStatsPlug -> AuthorizeSiteAccess
* Add email flow for ownership transfer
* Fix URLs in emails
* Fix small copy issues
* Make 'People' its own section in site settings
* Notify user via email if their access has been removed
* Check site lock status when invitation is accepted
* Check lock status when user subscribes
* Make sure only admins and owners can create shared links
* Changelog
* Add LockSites to daily cron
* Clean invitations after 48 hours
* Add notices about expiry
* Add invitation expired page
* Add doc link
