Updated reference documentation regarding GeoJsonModule.

Original pull request: #3539.
Closes #3517

Author: christophstrobl

src/main/asciidoc/reference/mongodb.adoc

@@ -1446,6 +1446,7 @@ The geo-near operations return a `GeoResults` wrapper object that encapsulates `
 
 MongoDB supports https://geojson.org/[GeoJSON] and simple (legacy) coordinate pairs for geospatial data. Those formats can both be used for storing as well as querying data. See the https://docs.mongodb.org/manual/core/2dsphere/#geospatial-indexes-store-geojson/[MongoDB manual on GeoJSON support] to learn about requirements and restrictions.
 
+[[mongo.geo-json.domain.classes]]
 ==== GeoJSON Types in Domain Classes
 
 Usage of https://geojson.org/[GeoJSON] types in domain classes is straightforward. The `org.springframework.data.mongodb.core.geo` package contains types such as `GeoJsonPoint`, `GeoJsonPolygon`, and others. These types are extend the existing `org.springframework.data.geo` types. The following example uses a `GeoJsonPoint`:
@@ -1469,6 +1470,7 @@ public class Store {
 ----
 ====
 
+[[mongo.geo-json.query-methods]]
 ==== GeoJSON Types in Repository Query Methods
 
 Using GeoJSON types as repository query parameters forces usage of the `$geometry` operator when creating the query, as the following example shows:
@@ -1529,6 +1531,7 @@ repo.findByLocationWithin(                              <4>
 <4> Use the legacy format `$polygon` operator.
 ====
 
+[[mongo.geo-json.metrics]]
 ==== Metrics and Distance calculation
 
 Then MongoDB `$geoNear` operator allows usage of a GeoJSON Point or legacy coordinate pairs.
@@ -1700,6 +1703,29 @@ Returning the 3 Documents just like the GeoJSON variant:
 <4> Distance from center point in _Kilometers_ - take it times 1000 to match _Meters_ of the GeoJSON variant.
 ====
 
+[[mongo.geo-json.jackson-modules]]
+==== GeoJSON Jackson Modules
+
+By using the <<core.web>>, Spring Data registers additional Jackson ``Modules``s to the `ObjectMapper` for deserializing common Spring Data domain types.
+Please refer to the <<core.web.basic.jackson-mappers>> section to learn more about the infrastructure setup of this feature.
+
+The MongoDB module additionally registers ``JsonDeserializer``s for the following GeoJSON types via its `GeoJsonConfiguration` exposing the `GeoJsonModule`.
+----
+org.springframework.data.mongodb.core.geo.GeoJsonPoint
+org.springframework.data.mongodb.core.geo.GeoJsonMultiPoint
+org.springframework.data.mongodb.core.geo.GeoJsonLineString
+org.springframework.data.mongodb.core.geo.GeoJsonMultiLineString
+org.springframework.data.mongodb.core.geo.GeoJsonPolygon
+org.springframework.data.mongodb.core.geo.GeoJsonMultiPolygon
+----
+
+[NOTE]
+====
+The `GeoJsonModule` only registers ``JsonDeserializer``s!
+
+The next major version (`4.0`) will register both, ``JsonDeserializer``s and ``JsonSerializer``s for GeoJSON types by default.
+====
+
 [[mongo.textsearch]]
 === Full-text Queries