Adding a guide for making raw json requests using the client

Signed-off-by: Vacha Shah <vachshah@amazon.com>

guides/json.md

@@ -0,0 +1,156 @@
+- [Making Raw JSON REST Requests](#making-raw-json-rest-requests)
+  - [GET](#get)
+  - [PUT](#put)
+  - [POST](#post)
+  - [DELETE](#delete)
+
+# Making Raw JSON REST Requests
+
+The OpenSearch client implements many high-level REST DSLs that invoke OpenSearch APIs. However you may find yourself in a situation that requires you to invoke an API that is not supported by the client. Use `client.Perform` to do so.
+
+## Setup
+
+Let's create a client instance:
+
+```go
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"strings"
+
+	"github.com/opensearch-project/opensearch-go/v2/opensearchapi"
+)
+
+func main() {
+	if err := example(); err != nil {
+		fmt.Println(fmt.Sprintf("Error: %s", err))
+		os.Exit(1)
+	}
+}
+
+func example() error {
+	client, err := opensearchapi.NewDefaultClient()
+	if err != nil {
+		return err
+	}
+```
+
+## GET
+
+The following example returns the server version information via `GET /`.
+
+```go
+	infoRequest, err := http.NewRequest("GET", "/", nil)
+	if err != nil {
+		return err
+	}
+
+	infoResponse, err := client.Client.Perform(infoRequest)
+	if err != nil {
+		return err
+	}
+
+	resBody, err := ioutil.ReadAll(infoResponse.Body)
+	if err != nil {
+		return err
+	}
+	fmt.Printf("client info: %s\n", resBody)
+```
+
+## PUT
+
+The following example creates an index.
+
+```go
+	var index_body = strings.NewReader(`{
+    "settings": {
+        "index": {
+            "number_of_shards": 2,
+            "number_of_replicas": 1
+        }
+    },
+    "mappings": {
+        "properties": {
+            "title": {
+                "type": "text"
+            },
+            "year": {
+                "type": "integer"
+            }
+        }
+    }
+}`)
+
+	createIndexRequest, err := http.NewRequest("PUT", "/movies", index_body)
+	if err != nil {
+		return err
+	}
+	createIndexRequest.Header["Content-Type"] = []string{"application/json"}
+	createIndexResp, err := client.Client.Perform(createIndexRequest)
+	if err != nil {
+		return err
+	}
+	createIndexRespBody, err := ioutil.ReadAll(createIndexResp.Body)
+	if err != nil {
+		return err
+	}
+	fmt.Println("create index: ", string(createIndexRespBody))
+```
+
+Note that the client will raise errors automatically. For example, if the index already exists, an error containing `resource_already_exists_exception` root cause will be thrown.
+
+## POST
+
+The following example searches for a document.
+
+```go
+	query := strings.NewReader(`{
+    "size": 5,
+    "query": {
+        "multi_match": {
+        "query": "miller",
+        "fields": ["title^2", "director"]
+        }
+    }
+}`)
+	searchRequest, err := http.NewRequest("POST", "/movies/_search", query)
+	if err != nil {
+		return err
+	}
+	searchRequest.Header["Content-Type"] = []string{"application/json"}
+	searchResp, err := client.Client.Perform(searchRequest)
+	if err != nil {
+		return err
+	}
+	searchRespBody, err := ioutil.ReadAll(searchResp.Body)
+	if err != nil {
+		return err
+	}
+	fmt.Println("search: ", string(searchRespBody))
+```
+
+## DELETE
+
+The following example deletes an index.
+
+```go
+	deleteIndexRequest, err := http.NewRequest("DELETE", "/movies", nil)
+	if err != nil {
+		return err
+	}
+	deleteIndexResp, err := client.Client.Perform(deleteIndexRequest)
+	if err != nil {
+		return err
+	}
+	deleteIndexRespBody, err := ioutil.ReadAll(deleteIndexResp.Body)
+	if err != nil {
+		return err
+	}
+	fmt.Println("delete index: ", string(deleteIndexRespBody))
+	return nil
+}
+```