Refactored type definitions (#1119)

* Updated types generation script

* Refactored api method definitions

* Updated test
- Removed old test code
- Added tsd dev dependency
- Rewritten test with tsd

* Removed unused dependencies

* Fixed definition

* Updated test

* Updated docs

* Improved events type definitions

* Updated test

* Minor fixes in the type definitons

* More type test

* Improved Transport type definitions

* Updated test

* Addressed comments

* Code generation

* Use RequestBody, Response and Context everywhere, also default Context to unknown

* Updated test

* body -> hasBody

* Fixed conflicts

* Updated code generation

* Improved request body type definition

* Updated code generation

* Use BodyType for both request and reponses generics
- Use extends for defining the RequestBody generic to force the user
  following the same shape.
- BodyType and NDBodyType now accepts a generics to allow injecting
  more specific types in the future

* API generation

* Updated test

* Updated docs

* Use BodyType also in ReponseError

* Removed useless client generics

* Renamed generics and types
- prefixed all generics with a T
- BodyType => RequestBody
- NDBodyType => RequestNDBody
- Added ResponseBody

* Updated test

* Updated docs

* Test ResponseBody as well

* Simplify overloads

* API generation

* Updated test

* Updated error types

docs/typescript.asciidoc

@@ -13,7 +13,14 @@ request for instance, you can access them via `RequestParams.Search`.
 Every API that supports a body, accepts a 
 https://www.typescriptlang.org/docs/handbook/generics.html[generics] which 
 represents the type of the request body, if you don't configure anything, it 
-will default to `any`.
+will default to `RequestBody`. +
+`RequestBody`, along with `RequestNDBody` and `ResponseBody` are defined inside the client, and it looks like this:
+[source,ts]
+----
+type RequestBody<T = Record<string, any>> = T | string | Buffer | ReadableStream
+type RequestNDBody<T = Record<string, any>[]> = T | string[] | Buffer | ReadableStream
+type ResponseBody<T = Record<string, any>> = T | string | boolean | ReadableStream
+----
 
 For example:
 
@@ -49,7 +56,7 @@ const searchParams: RequestParams.Search = {
 
 You can find the type definiton of a response in `ApiResponse`, which accepts a 
 generics as well if you want to specify the body type, otherwise it defaults to 
-`any`.
+`BodyType`.
 
 [source,ts]
 ----
@@ -137,19 +144,43 @@ interface Source {
   foo: string
 }
 
-async function run (): Promise<void> {
-  // Define the search parameters
-  const searchParams: RequestParams.Search<SearchBody> = {
+async function run () {
+  // All of the examples below are valid code, by default,
+  // the request body will be `RequestBody` and response will be `ResponseBody`.
+  const response = await client.search({
     index: 'test',
     body: {
       query: {
         match: { foo: 'bar' }
       }
     }
-  }
+  })
+  // body here is `ResponseBody`
+  console.log(response.body)
 
-  // Craft the final type definition
-  const response: ApiResponse<SearchResponse<Source>> = await client.search(searchParams)
+  // The first generic is the request body
+  const response = await client.search<SearchBody>({
+    index: 'test',
+    // Here the body must follow the `SearchBody` interface
+    body: {
+      query: {
+        match: { foo: 'bar' }
+      }
+    }
+  })
+  // body here is `ResponseBody`
+  console.log(response.body)
+
+  const response = await client.search<SearchBody, SearchResponse<Source>>({
+    index: 'test',
+    // Here the body must follow the `SearchBody` interface
+    body: {
+      query: {
+        match: { foo: 'bar' }
+      }
+    }
+  })
+  // Now you can have full type definition of the response
   console.log(response.body)
 }