Merge pull request #806 from telefonicaid/task/add-ngsi-patching-id-type

Add NGSI patching type and id documentation

docs/usermanual.md

@@ -116,10 +116,47 @@ tools available online like [this one](https://string-functions.com/string-hex.a
 
 It is possible report as a measure a NGSI-v2 or NGSI-LD payload when related device/group is configured with
 `payloadType` `ngsiv2` or `ngsild`. In these cases payload is ingested as measure where entity attributes are measure
-attributes and `id` and `type` are ignored, since `id` and `type` from device/group configuration provisioned are used,
-as well as `actionType`.
+attributes.
 
-Examples of these `ngsiv2` payloads are the following ones:
+Note that the entity ID and type in the measure are also include as attributes `measure_id` and `measure_type` as described 
+[here](https://github.dev/telefonicaid/iotagent-node-lib/doc/api.md#special-measures-and-attributes-names) (both using 
+attribute type `Text`). The ID and type of the entity updated at Context Broker is taken from device/group configuration or provision,
+
+However, it is possible to use the same entity ID that the original one by using `entityNameExp` 
+at [device group provision](https://github.com/telefonicaid/iotagent-node-lib/blob/master/doc/api.md#config-group-datamodel), this way:
+
+```
+"entityNameExp": "measure_id"
+```
+
+The `actionType` used in the update sent to Context Broker is taken from the measure in the case that measure corresponds to
+a NGSI-v2 batch update. In other cases (i.e. NGSI-LD or NGSI-v2 non-batch update), the `actionType` is the default one (`append`).
+
+For instance, given an incoming **measure** as the follwing one:
+
+```json
+{
+    "id": "MyEntityId1",
+    "type": "MyEntityType1",
+    "attr1": { "type": "Text", "value": "MyAttr1Value"}
+}
+```
+
+It would persist an entity into the Context Broker like the following one:
+
+```json
+{
+    "id":"MyProvisionID",
+    "type":"MyProvisionType",
+    "attr1": { "type": "Text", "value": "MyAttr1Value"},
+    "measure_id": {"type": "Text","value": "MyEntityId1"},
+    "measure_type":{"type": "Text","value": "MyEntityType1"}
+}
+```
+
+The IoTA is able to ingest different types of `NGSI-V2` and `NGSI-LD` payloads like the following ones:
+
+**NGSI-V2**
 
 (1) NGSI-v2 batch update format:
 
@@ -171,7 +208,7 @@ Examples of these `ngsiv2` payloads are the following ones:
 }
 ```
 
-Example of these `ngsild` payloads are the following ones:
+**NGSI-LD**
 
 (1) NGSI-LD entities array format: