Waldur-core

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- Implement management command for cleaning up stale event types in hooks and system notifications.
- Rewrite hook summary view using SummaryQuerySet.
- Allow quotas to raise errors if their usage is over limit.
- Fix monitoring_items serializer.
- Verify VAT number using VIES checker and store it database.
- Fix filtering historic resources by customer.

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- Enable filtering shared service settings.
- Implement service-specific statistics endpoint.
- Rewrite service summary view using SummaryQueryset.
- Fix TLS support for Elasticsearch connections.

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- Bugfix.

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- Introduced ApplicationMixin for tracking Application resources.
- Bugfixes.

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- Expose groups for event types and alert types.
- Added group types for alerts and events.
- Cleaned up OpenStack dependencies from core.
- Bugfixes.

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- Added expiration time to authorization tokens.
- Fix filtering events by scope_type and time range.
- Implemented custom provider pricing configuration.
- Add filtering of resources by service counters by user visibility.
- Fixed push notifications through GCM.
- Bugfixes.