[DOCS] [Monitoring] Document License Change Impact

[pickypg]

Due to the changing of how licensing worked in 6.3, versus earlier releases of 6.x, it had an impact on the pre-6.3 Monitoring UI's ability to display 6.3+ clusters. (Lots of versions here, but suffice to say that 6.0 - 6.2 monitoring UI cannot display 6.3+ clusters)

We have always said that the monitoring cluster should be upgraded first, but it may catch people off guard that it claims a licensing issue. As such, I am not really sure what all or even where we would want to document this since it's not really a breaking change due to that requirement. It may be enough to just have this issue and close it.

[pickypg]

/cc @lcawl @GlenRSmith

[lcawl]

@pickypg When you say it claims a licensing issue, do you mean that there are particular (licensing) errors that occur? If so, we could create troubleshooting information for those errors.

[pickypg]

Yes, it should show a banner error (along the top):

You can't view the "${this.props.cluster_name}" cluster because the license information is invalid.

Naturally the variable would be replaced. That's the tip off that it's happening here.

[lcawl]

There's a troubleshooting page being created for #18958 so this could be added there.