Fix/explicit attributes true: just measures in active attrs and active attrs with expressions

[AlvaroVega]

• Add more tests about explicitAttributes: true

[mapedraza]

LGTM

[fgalan]

This behaviour match the one described in documentation?

[mapedraza]

According to this:

iotagent-node-lib/doc/advanced-topics.md

Lines 301 to 309 in ea48c80

	### Explicitly defined attributes (explicitAttrs)
	If a given measure element (object_id) is not defined in the mappings of the device or group provision, the measure is
	stored in the Context Broker by adding a new attribute to the entity with the same name of the undefined measure
	element. By adding the field `explicitAttrs` with `true` value to device or group provision, the IoTAgent rejects the
	measure elements that are not defined in the mappings of device or group provision, persisting only the one defined in
	the mappings of the provision. If `explicitAttrs` is provided both at device and group level, the device level takes
	precedence. Additionally `explicitAttrs` can be used to define which meassures (identified by their attribute names, not
	by their object_id) defined in JSON/JEXL array will be propagated to NGSI interface.

the IoTAgent rejects the measure elements that are not defined in the mappings of device or group provision

From my perspective, yes, it involves that case (since they are defined in the provision)

[AlvaroVega]

https://github.com/telefonicaid/iotagent-node-lib/blob/master/doc/advanced-topics.md#explicitly-defined-attributes-explicitattrs

Case 2:

"explicitAttrs": true

just measures defined in active, static (plus conditionally TimeInstant) will be propagated to NGSI interface.

[mapedraza]

So, no further changes required in the documentation

[fgalan]

NTC

[fgalan]

LGTM