Reopen of #10475: dynamic modification of OTEL Resource Attributes (via Content Modifier or LUA)

[ErmakovDmitriy]

Is your feature request related to a problem? Please describe.
This is reopening of an automatically closed issue (#10475).

I would like to be able to modify otel_resource_attributes dynamically, based on
a log message data.
This is useful in case the messages come from non-OTEL source and I want to
use FluentBit to make them OTEL-compatible and send further.

For example, if we have Kubernetes container logs, it would be nice to put some Kubernetes metadata in otel_resource_attributes
such as pod namespace, name, container name.

Describe the solution you'd like

It would be nice to be able to use content_modifier as below (example is borrowed from the closed issue):

inputs:
      # Receiving forwarded
      # messages from a remote
      # FluentBit which has input "systemd"
    - name: forward
      listen: 0.0.0.0
      port: 24224

      processors:
        logs:
          - name: opentelemetry_envelope
          - name: lua
            # Some LUA record modifications
            # which will define additional log_record.resource_attributes
            # data based on information from the Log message.
          - name: content_modifier
            context: otel_resource_attributes
            # Here it would be really nice not only extract
            # the data using RecordAccessor
            # but also "upsert" (or replace) the whole 
            # otel_resource_attributes context data.
            action: upsert
            value: log_record.resource_attributes

or somehow modify the resource.attributes from LUA.

Describe alternatives you've considered

I have considered using LUA to set OTEL resource attributes (it would actually be nice to be able to use LUA to modify any OTEL contexts (https://docs.fluentbit.io/manual/4.0/data-pipeline/processors/content-modifier#opentelemetry-contexts) but it doesn't seem to be possible now.

Additional context