feat: Add Terraform provider API client with HTTP methods and provider configuration

- Add APIClient struct with BaseURL, APIKey, and HTTPClient with 30s timeout
- Add providerConfigure to initialize client from schema with api_url and api_key
- Add doRequest helper with context support, JSON marshaling, Content-Type and Authorization headers
- Add get method accepting GET requests with 200 OK validation and JSON decoding
- Add post method accepting POST requests with 200/201 status validation and optional

terraform/provider/client.go

@@ -0,0 +1,122 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/hashicorp/terraform-plugin-sdk/v2/diag"
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+)
+
+// APIClient is the HTTP client for the Telecom API
+type APIClient struct {
+	BaseURL    string
+	APIKey     string
+	HTTPClient *http.Client
+}
+
+func providerConfigure(ctx context.Context, d *schema.ResourceData) (interface{}, diag.Diagnostics) {
+	apiURL := d.Get("api_url").(string)
+	apiKey := d.Get("api_key").(string)
+
+	client := &APIClient{
+		BaseURL: apiURL,
+		APIKey:  apiKey,
+		HTTPClient: &http.Client{
+			Timeout: 30 * time.Second,
+		},
+	}
+
+	return client, nil
+}
+
+func (c *APIClient) doRequest(ctx context.Context, method, path string, body interface{}) (*http.Response, error) {
+	var reqBody *bytes.Buffer
+	if body != nil {
+		jsonBody, err := json.Marshal(body)
+		if err != nil {
+			return nil, fmt.Errorf("failed to marshal request body: %w", err)
+		}
+		reqBody = bytes.NewBuffer(jsonBody)
+	} else {
+		reqBody = bytes.NewBuffer(nil)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, method, c.BaseURL+path, reqBody)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	if c.APIKey != "" {
+		req.Header.Set("Authorization", "Bearer "+c.APIKey)
+	}
+
+	return c.HTTPClient.Do(req)
+}
+
+func (c *APIClient) get(ctx context.Context, path string, result interface{}) error {
+	resp, err := c.doRequest(ctx, http.MethodGet, path, nil)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("API returned status %d for GET %s", resp.StatusCode, path)
+	}
+
+	return json.NewDecoder(resp.Body).Decode(result)
+}
+
+func (c *APIClient) post(ctx context.Context, path string, body, result interface{}) error {
+	resp, err := c.doRequest(ctx, http.MethodPost, path, body)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated {
+		return fmt.Errorf("API returned status %d for POST %s", resp.StatusCode, path)
+	}
+
+	if result != nil {
+		return json.NewDecoder(resp.Body).Decode(result)
+	}
+	return nil
+}
+
+func (c *APIClient) put(ctx context.Context, path string, body, result interface{}) error {
+	resp, err := c.doRequest(ctx, http.MethodPut, path, body)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("API returned status %d for PUT %s", resp.StatusCode, path)
+	}
+
+	if result != nil {
+		return json.NewDecoder(resp.Body).Decode(result)
+	}
+	return nil
+}
+
+func (c *APIClient) delete(ctx context.Context, path string) error {
+	resp, err := c.doRequest(ctx, http.MethodDelete, path, nil)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusNoContent {
+		return fmt.Errorf("API returned status %d for DELETE %s", resp.StatusCode, path)
+	}
+
+	return nil
+}