Add JSON processor documentation

_ingest-pipelines/processors/json.md

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+---
+layout: default
+title: JSON
+parent: Ingest processors
+nav_order: 170
+---
+
+# JSON processor
+
+The `json` processor serializes a string-valued field into a map of maps, which can be useful for various data processing and enrichment tasks.
+
+The following is the syntax for the `json` processor:
+
+```json
+{
+  "processor": {
+    "json": {
+      "field": "<field_name>",
+      "target_field": "<target_field_name>",
+      "add_to_root": <boolean>
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Configuration parameters
+
+The following table lists the required and optional parameters for the `json` processor.
+
+Parameter | Required/Optional | Description |
+|-----------|-----------|-----------|
+`field` | Required | The name of the field containing the JSON-formatted string to be deserialized.
+`target_field` | Optional | The name of the field where the deserialized JSON data will be stored. If this parameter is not provided, the deserialized data is added to the root of the document.
+`add_to_root` | Optional | A boolean flag that determines whether the deserialized JSON data should be added to the root of the document (`true`) or stored in the target_field (`false`). Default value is `false`. 
+`description` | Optional | A description of the processor's purpose or configuration.
+`if` | Optional | Specifies to conditionally execute the processor.
+`ignore_failure` | Optional | Specifies to ignore failures for the processor. See [Handling pipeline failures]({{site.url}}{{site.baseurl}}/ingest-pipelines/pipeline-failures/).
+`on_failure`| Optional | Specifies a list of processors to run if the processor fails during execution. These processors are executed in the order they are specified. 
+`tag` | Optional | An identifier tag for the processor. Useful for debugging in order to distinguish between processors of the same type.
+
+## Using the processor
+
+Follow these steps to use the processor in a pipeline.
+
+### Step 1: Create a pipeline
+
+The following query creates a pipeline named `my-json-pipeline` that uses the `json` processor to process JSON data and enrich the documents with additional information: 
+
+```json
+PUT _ingest/pipeline/my-json-pipeline
+{
+  "description": "Example pipeline using the JsonProcessor",
+  "processors": [
+    {
+      "json": {
+        "field": "raw_data",
+        "target_field": "parsed_data",
+        "add_to_root": false,
+        "on_failure": [
+          {
+            "set": {
+              "field": "error_message",
+              "value": "Failed to parse JSON data"
+            }
+          },
+          {
+            "fail": {
+              "message": "Failed to process JSON data"
+            }
+          }
+        ]
+      }
+    },
+    {
+      "set": {
+        "field": "processed_timestamp",
+        "value": "{{_ingest.timestamp}}"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+### Step 2 (Optional): Test the pipeline
+
+It is recommended that you test your pipeline before you ingest documents.
+{: .tip}
+
+To test the pipeline, run the following query:
+
+```json
+POST _ingest/pipeline/my-json-pipeline/_simulate
+{
+  "docs": [
+    {
+      "_source": {
+        "raw_data": "{\"name\":\"John\",\"age\":30,\"city\":\"New York\"}"
+      }
+    },
+    {
+      "_source": {
+        "raw_data": "{\"name\":\"Jane\",\"age\":25,\"city\":\"Los Angeles\"}"
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+The following example response confirms that the pipeline is working as expected:
+
+```json
+{
+  "docs": [
+    {
+      "doc": {
+        "_index": "_index",
+        "_id": "_id",
+        "_source": {
+          "processed_timestamp": "2024-05-30T15:24:48.064472090Z",
+          "raw_data": """{"name":"John","age":30,"city":"New York"}""",
+          "parsed_data": {
+            "name": "John",
+            "city": "New York",
+            "age": 30
+          }
+        },
+        "_ingest": {
+          "timestamp": "2024-05-30T15:24:48.06447209Z"
+        }
+      }
+    },
+    {
+      "doc": {
+        "_index": "_index",
+        "_id": "_id",
+        "_source": {
+          "processed_timestamp": "2024-05-30T15:24:48.064543006Z",
+          "raw_data": """{"name":"Jane","age":25,"city":"Los Angeles"}""",
+          "parsed_data": {
+            "name": "Jane",
+            "city": "Los Angeles",
+            "age": 25
+          }
+        },
+        "_ingest": {
+          "timestamp": "2024-05-30T15:24:48.064543006Z"
+        }
+      }
+    }
+  ]
+}
+```
+{% include copy-curl.html %}
+
+### Step 3: Ingest a document 
+
+The following query ingests a document into an index named `my-index`:
+
+```json
+POST my-index/_doc?pipeline=my-json-pipeline
+{
+  "raw_data": "{\"name\":\"John\",\"age\":30,\"city\":\"New York\"}"
+}
+```
+{% include copy-curl.html %}
+
+#### Response
+
+This response confirms that the document with the JSON data from the `raw_data` field was successfully indexed:
+
+```json
+{
+  "_index": "my-index",
+  "_id": "mo8yyo8BwFahnwl9WpxG",
+  "_version": 1,
+  "result": "created",
+  "_shards": {
+    "total": 2,
+    "successful": 1,
+    "failed": 0
+  },
+  "_seq_no": 3,
+  "_primary_term": 2
+}
+```
+{% include copy-curl.html %}
+
+### Step 4 (Optional): Retrieve the document
+
+To retrieve the document, run the following query:
+
+```json
+GET my-index/_doc/1
+```
+{% include copy-curl.html %}