Manual Monitors

**Is your feature request related to a problem? Please describe.**
A fully manual monitor

**Describe the solution you'd like**
Preset or custom option such as "operational", "degraded", "partial outage" and "outage" with a simple picker to choose the current state

**Describe alternatives you've considered**
Cachet

Look at the existing monitor types in the codebase to understand how states are defined and persisted. The UI likely has a component for selecting monitor types and setting their status. Check for models related to monitors and their state transitions. Implementing a new monitor type will require changes in both the backend data model and the frontend picker interface.

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