Add SOH channels to SQUAC and allow them to be selected in a Channel Group

[jrhartog]

This will require quite some changes and we should think through the use cases before we make a change.

• We need to decide which SOH channels
• We then need to include those channel codes in the job that updates channels in the SQUAC DB using FDSN Web Services
• If we do this, we may want a toggle on the Channel Group page that says "also show SOH channels" or something similar.
• The "default" channel group for a single station should include the SOH channels as well as the seismic or other channels (e.g. infrasound pressure, or downhole pressure).
• A decision on how granular we want the SOH data to go into the DB. Many have a sample rate of once a minute.

[alexhutko]

The simpler way is to create a new metric and park it on the Z component of a station. That may not be ideal, but SOH channels, as I understand them, don't have much we are interested in other than their value, i.e. we don't really care what the power at 10Hz is of a water pump. That means a standard metric like mean/max amplitude or total duration of non-zero time would suffice. Either way, a new metric would be added.

"A decision on how granular we want the SOH data to go into the DB. Many have a sample rate of once a minute."
Does this suggest we'd basically upload all values to the squac db for some things? That changes how squac gets used to some extent.

Understanding the use case(s) you had in mine and if this is to mimic/replace nagios will help guide these issues.