Ensure "replace" mode chart deletes old data

[Steve-Mcl]

Description

• Add a deleteMessages mutation to remove old data from datastore
• dont let chart animate or raise events when clearing

Before

After

Demo flow for testing

Demo flow is in the issue

Related Issue(s)

closes #1899

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[Steve-Mcl]

@colinl would you be in a position review and test this in various forms and see if it improves matters for you?

[colinl]

I am on holiday so might not have time to look at it properly for a few days.

There is a separate issue that I have been looking at, that if data is being regularly added to the chart, and X Axis limit is set to a time, that the data is not stripped off the front of the chart as new data is added at the end. This is a browser only issue I think as switching to a different page and back again does remove the old data. The fundamental issue is that in the vue file in limitDataSize, the line
if (cutoff && d.x < cutoff) {
should be
if (cutoff && d[0] < cutoff) {
However, I am not sure it is simply a matter of changing that, as I think that then if a batch of historical timestamped data were added then that might immediately be removed as it is older than the config spec, though I have not confirmed that this is the case.
Probably this can be considered a separate issue though, so I will concentrate on this PR when I do have some time.

[colinl]

Starting to look at it now.
Is this already handled correctly server side?

[Steve-Mcl]

Is this already handled correctly server side

I have a distant memory that it is replaced in back end (but it's worth a double check)

[colinl]

Answering that myself, it seems that it is already handled in the server.

[colinl]

OK, it all looks good to me, given my rather limited knowledge of how the data store works.