Promgen

- [INTERNAL] Upgrade to Django 2.2.x 152
- [BUGFIX] Fix rule rendering table on host detail page 151
- [BUGFIX] Fix rendering errors with Silence/Alert dropdowns 150
- [BUGFIX] Fix search page rendering 149
- [INTERNAL] Move remaining celery tasks to tasks.py 139

- [CHANGE] Refactor shard assignment from service to Project 147

- [BUGFIX] Refactor rule validation to take into account labels and annotations 144
- [BUGFIX] Move promtool validation into RuleForm.clean 142
- [INTERNAL] Update various dependencies 143
- [IMPROVEMENT] Add proxy for /api/v1/labels 140
- [IMPROVEMENT] Use django-filters for api filtering 126

This release adds support for filters for notifications. Alerts can be filtered so that different notification targets can be restricted by label. For example, sending urgent messages directly to LINE but sending less urgent messages to be logged to slack

- [INTERNAL] Refactor how we proxy errors 136
- [BUGFIX] Fix arguments for create/filter/get_or_create 137
- [BUGFIX] Fix filterActiveSilences condition 135
- [FEATURE] Implement sender whitelist filters 132
- [INTERNAL] Refactor Breadcrumb from template to simple_tag 133
- [INTERNAL] Refactor manager class and validators 131

- [BUGFIX] Fix computed labels 129
- [BUGFIX] Fix validation of silence duration 130
- [IMPROVEMENT] Add logo + favicon 128
- [IMPROVEMENT] Various page query optimizations 127

- [IMPROVEMENT] Add button to silence a single alert 125
- [CHANGES] Rewritten display of alerts and silences to use vuejs 124
- [INTERNAL] Split proxy views to their own module 123
- [IMPROVEMENT] Add default notifier when subscribing 122
- [BUGFIX] Validate URL field for notifications 121
- [ENHANCEMENT] Improvements to Admin Alert view 116