Function mergeSpanAttributes

mergeSpanAttributes(
sources: Iterable<ModbusSpanAttributes | undefined>,
): ModbusSpanAttributes
Joins the attributes of every caller in one batch.

A batch carries several callers' worth of vocabulary, and the keys are opaque, so a repeated key keeps every value rather than letting one silently win. The values are joined with a comma, the same shape the library uses for its own modbus.unit_ids.

A batch of one is unaffected: a one-element join is the value itself.
Parameters
- sources: Iterable<ModbusSpanAttributes | undefined>
  One attribute record per caller. undefined entries are skipped.
Returns ModbusSpanAttributes
One record, with each key's values joined in first-seen order.
Example
```
mergeSpanAttributes([{ 'app.point': 'Supply' }, { 'app.point': 'Exhaust' }]);
// { 'app.point': 'Supply,Exhaust' }
```
- Defined in src/span-attributes.ts:36