feat: changes API and removes bloated interface.

Signed-off-by: Dmitry Kisler <admin@dkisler.com>

CHANGELOG.md

@@ -5,6 +5,39 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [v0.3.0] - 2023-10-26
+
+### Changed
+
+- The interface `Client` is removed and the output of the `NewClient` is the pointer to the struct now. It will facilitate stub of the SDK client.
+- [**BREAKING**] `NewClient` requires `Config` to initialise a Neon client. It's meant to improve security by eliminating
+  support of environment variables for authentication by default. It also simplifies the codebase.
+
+  **Example**
+  ```go
+  package main
+
+  import (
+        "log"
+
+        neon "github.com/kislerdm/neon-sdk-go"
+  )
+
+  func main() {
+        client, err := neon.NewClient(neon.Config{Key: "{{.NeonApiKey}}"})
+        if err != nil {
+            panic(err)
+        }
+
+        v, err := client.ListProjects()
+        if err != nil {
+            panic(err)
+        }
+
+        log.Printf("%d projects found", len(v.Projects))
+  }
+  ```
+
 ## [v0.2.5] - 2023-10-22
 
 The release incorporates the up-to-date [API contract](openAPIDefinition.json) as of 2023-10-11 00:08:16 GMT.

README.md

@@ -51,19 +51,9 @@ Where `{{.Ver}}` is the release version.
 
 ### Code Snippets
 
-#### Authentication
+### Default HTTP Client
 
-Authentication with the Neon Platform is implemented
-using [variadic functions](https://gobyexample.com/variadic-functions) and environment variables evaluation in the
-following order:
-
-1. Variadic function client's argument;
-2. Environment variable `NEON_API_KEY`.
-
-Note that if the API key is provided as the variadic function argument, key from the environment variable `NEON_API_KEY`
-will be ignored.
-
-##### Variadic Function
+The following snippet demonstrates how to initialize SDK which will use default HTTP client. 
 
 ```go
 package main
@@ -75,7 +65,7 @@ import (
 )
 
 func main() {
-	client, err := neon.NewClient(neon.WithAPIKey("{{.NeonApiKey}}"))
+	client, err := neon.NewClient(neon.Config{Key: "{{.NeonApiKey}}"})
 	if err != nil {
 		panic(err)
 	}
@@ -89,22 +79,25 @@ func main() {
 }
 ```
 
-##### Environment Variables Evaluation
+### Custom HTTP client
 
-**_Requirement_**: a valid Neon [API key](https://neon.tech/docs/manage/api-keys/) must be exported as the environment
-variable `NEON_API_KEY`.
+The SDK can initialized with a custom HTTP client.
 
 ```go
 package main
 
 import (
+	"net/http"
 	"log"
+	"time"
 
 	neon "github.com/kislerdm/neon-sdk-go"
 )
 
 func main() {
-	client, err := neon.NewClient()
+	myHTTPClient := &http.Client{Timeout: 30 * time.Second}
+
+	client, err := neon.NewClient(neon.Config{Key: "{{.NeonApiKey}}", HTTPClient: myHTTPClient})
 	if err != nil {
 		panic(err)
 	}
@@ -132,7 +125,7 @@ import (
 )
 
 func main() {
-	client, err := neon.NewClient(neon.WithHTTPClient(neon.NewMockHTTPClient()))
+	client, err := neon.NewClient(neon.Config{HTTPClient: neon.NewMockHTTPClient()})
 	if err != nil {
 		panic(err)
 	}

acc_test.go

@@ -5,14 +5,15 @@ package sdk_test
 
 import (
 	"fmt"
+	"os"
 	"testing"
 	"time"
 
 	sdk "github.com/kislerdm/neon-sdk-go"
 )
 
 func TestSmoke(t *testing.T) {
-	cl, err := sdk.NewClient()
+	cl, err := sdk.NewClient(sdk.Config{Key: os.Getenv("NEON_API_KEY")})
 	if err != nil {
 		t.Fatalf("cannot initialise SDK: %v", err)
 	}

doc.go

@@ -2,7 +2,7 @@
 
 Find more about the service: https://neon.tech/docs/introduction.
 
-Author: dkisler.com
+Author: Dmitry Kisler <https://www.dkisler.com>
 
 */
 

error.go

@@ -0,0 +1,60 @@
+package sdk
+
+import (
+	"bytes"
+	"encoding/json"
+	"io"
+	"net/http"
+	"strconv"
+)
+
+// Error API error.
+type Error struct {
+	HTTPCode int
+	errorResp
+}
+
+func (e Error) Error() string {
+	return "[HTTP Code: " + strconv.Itoa(e.HTTPCode) + "][Error Code: " + e.Code + "] " + e.Message
+}
+
+func (e Error) httpResp() *http.Response {
+	o, _ := json.Marshal(e.errorResp)
+	return &http.Response{
+		Status:        e.Code,
+		StatusCode:    e.HTTPCode,
+		Body:          io.NopCloser(bytes.NewReader(o)),
+		ContentLength: int64(len(o)),
+	}
+}
+
+type errorResp struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+func convertErrorResponse(res *http.Response) error {
+	var v errorResp
+	buf, err := io.ReadAll(res.Body)
+	defer func() { _ = res.Body.Close() }()
+	if err != nil {
+		return Error{
+			HTTPCode: res.StatusCode,
+			errorResp: errorResp{
+				Message: "cannot read response bytes",
+			},
+		}
+	}
+	if err := json.Unmarshal(buf, &v); err != nil {
+		return Error{
+			HTTPCode: res.StatusCode,
+			errorResp: errorResp{
+				Message: err.Error(),
+			},
+		}
+	}
+	return Error{
+		HTTPCode:  res.StatusCode,
+		errorResp: v,
+	}
+}