Summary

Related to the Java agent implementing messaging data (elastic/apm#143), we want to add those fields to the metadata tab (when available).

Field names in elasticsearch:

• transaction.message
• span.message

Solution

• Add new Message section to the metadata table for Transactions and Spans
  • Transactions: Add it between Process and Agent sections https://github.com/elastic/kibana/blob/master/x-pack/legacy/plugins/apm/public/components/shared/MetadataTable/TransactionMetadata/sections.ts#L7
  • Spans: Add it between Service and Agent sections https://github.com/elastic/kibana/blob/master/x-pack/legacy/plugins/apm/public/components/shared/MetadataTable/SpanMetadata/sections.ts#L17
• For context.message.age.ms, we expect the calculation to be an estimate more than an accurate measurement; therefore we need to treat 0 and possibly surrounding values (negative and positive) as ~0. Please refer to the original comment in the meta issue. (postponed for the first iteration)