[FEATURE] Add native JSON support

[dblock]

Is your feature request related to a problem?

Ingesting a document today requires supplying it as an IoReader. Starting with an example in https://xeiaso.net/blog/elasticsearch:

data, err := json.Marshal(esEntry)
if err != nil {
	log.Fatalf("failed to marshal entry: %v", err)
}

resp, err := es.Index("site-search-kb", bytes.NewBuffer(data), es.Index.WithDocumentID(entry.ID))

Ugh.

What solution would you like?

Automatically marshal objects to/from JSON. Starting with the canonical example from https://go.dev/blog/json I think I want something that doesn't say "IoStreams" everywhere.

m := Message{"Alice", "Hello", 1294706395881547000}
es.Index("site-search-kb", m, es.Index.WithDocumentID(1))

Do you have any additional context?

Came from https://xeiaso.net/blog/elasticsearch

[dblock]

@Jakob3xD would love your thoughts!

[Jakob3xD]

Is a valid feature. Should be relative simple to implement, by making the requests bodys given to the function as arg an interface and the Marshal it.

[YuyaAbo]

I went through the code to understand the Issue and found opensearchutil.NewJSONReader. Is this sufficient to resolve the Issue? Is it enough to resolve the Issue or is there some functionality missing?

This utility function seems to be used as follows.

opensearch-go/opensearchutil/json_reader_integration_test.go

Lines 55 to 62 in c04e36a

	doc := struct {
	Title string `json:"title"`
	}{Title: "Foo Bar"}
	res, err = client.Index("test", opensearchutil.NewJSONReader(&doc), client.Index.WithRefresh("true"))
	if err != nil {
	t.Fatalf("Error getting response: %s", err)
	}

[dblock]

@YuyaAbo Thank you!

1. Can this be somehow automatic? In this case this would be a feature request.
2. Do we document this anywhere? Either way we should document this in the user guide, then we can close this. Would you like to help?

[YuyaAbo]

@dblock Yes, it would certainly be a useful addition if it could be automated.

I will add an introduction to opensearchutil.NewJSONReader to the user guide. I will send a PR later.

We will leave this issue as is for the purpose of adding functionality.

[tannerjones4075]

Should this issue be closed? #341 seems to have committed a merge request to add the functionality unless I am mistaken.

[dblock]

Yes, closing.