Mdb overrides subscription

[shefalijoshi]

Closes VIPEROMCT-295

Describe your changes:

Adds the subscribeToLimits API to the realtime provider
This subscribes to the type mdb-changes and returns any limits that have changed.

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[jvigliotta]

Hey! Nice! I've got a couple small questions/suggestions.

[shefalijoshi]

Testing Instructions:

• Create an overlay plot in Open MCT
• Add an endpoint that has no limits setup to this overlay plot
• Edit the overlay plot and enable limit lines
• Using the yamcs API, create an alarm at runtime for the endpoint above (For Quickstart use yamcs version >5.8.2)

Example: 
http://0.0.0.0:8090/api/mdb-overrides/<yamcs-instance>/realtime/parameters/<parameter-name>
{
    action: SET_DEFAULT_ALARMS,
    defaultAlarm: {
        minViolations: 1,
        staticAlarmRange: [
            {
            level: WATCH,
            minInclusive: 18,
            maxInclusive: 26
            }
        ]
    }
}

• The overlay plot in Open MCT should now show the new limits drawn.
• Remove the limit or change it using the yamcs API
• The overlay plot in Open MCT should now show the change.

[jvigliotta]

Nice! I have one more question that I think may be an existing issue in other subscription providers as well (definitely main realtime provider).

[akhenry]

Looks great! Just needs some tests. The same tests can verify both nasa/openmct#6735 and this.

[akhenry]

Have done some testing in our test environment. The changes work for catching limit changes immediately as they happen via subscription, but they do not resolve mdb overrides on load.

The limit-provider needs to also make a call to https://github.com/akhenry/openmct-yamcs/pull/333/files#diff-4a950de5fe10da4e7dff6cde433a8e4e90c4a1b606c6bb3919b79661c3302997L101 to resolve any MDB overrides on plot load.

[jvigliotta]

Looks good!

[unlikelyzero]

if you can remove this, we should. Not a big deal to print diagnostic to screen in tests

[jvigliotta]

Verified (Overlay Plots) - Testathon - 7/20/23
Looks great! I was able to set the limits using our script. The limits show up in the Overlay Plot where I set them. I can update the limits and they update in realtime without a refresh. I'm also able to enable and disable with the expected results.

Not sure if it's working for gauges or if that was a requirement. Not seeing anything there.