Splunk metric names should be validated via regex

[spiffyy99]

Component(s)

internal/splunk

Describe the issue you're reporting

Currently, while parsing splunk metric fields from events (starting with metric_name), no validation is done to ensure the metric names actually fit with Splunk criteria. According to the Splunk documentation, metric names have the following restriction:

Metric names can include only upper-case letters, lower-case letters, numbers, underscores, dots, and colon symbols.
Metric names cannot include spaces or the reserved term metric_name. Metric names cannot begin with numbers or underscores.

It follows that field names that don't follow this convention should be designated as dimensions rather than metric datapoints.

[github-actions]

Pinging code owners:

• internal/splunk: @dmitryax

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[crobert-1]

Hello @spiffyy99, thanks for filing! Since #34291 has been merged, can we close this issue?

[spiffyy99]

yes, i'll close it now. thanks for the review.

[crobert-1]

Thanks for resolving, really appreciate the help!