feat(whatsapp): 🎉 Add extended sending and template management

* Implemented new endpoints for sending various message types:
  - Audio
  - Sticker
  - Location
  - Contacts
  - Interactive messages
  - Template messages
  - Flow messages
  - Reactions
  - Marking messages as read

* Added template management endpoints:
  - List templates
  - Upload templates
  - Delete templates

* Introduced flow management endpoints:
  - List flows
  - Create flows
  - Get flow details
  - Upload flow assets
  - Publish flows
  - Delete flows

* Added phone number management endpoints:
  - List phone numbers
  - Request verification code
  - Verify code

* Enhanced media management with delete media endpoint.

* Updated dependencies.

pkg/whatsapp/businessapi/helpers.go

@@ -0,0 +1,171 @@
+package businessapi
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"net/url"
+)
+
+// graphAPIGet performs an authenticated GET to the Graph API and unmarshals the response.
+func (c *Client) graphAPIGet(ctx context.Context, path string, params url.Values, result any) error {
+	u := fmt.Sprintf("https://graph.facebook.com/%s/%s", c.config.APIVersion, path)
+	if len(params) > 0 {
+		u += "?" + params.Encode()
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "GET", u, nil)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.config.AccessToken)
+
+	return c.executeRequest(req, result)
+}
+
+// graphAPIPost performs an authenticated POST with a JSON body.
+// body may be nil for action-only endpoints (e.g. publish a flow).
+func (c *Client) graphAPIPost(ctx context.Context, path string, body any, result any) error {
+	u := fmt.Sprintf("https://graph.facebook.com/%s/%s", c.config.APIVersion, path)
+
+	var reqBody io.Reader
+	if body != nil {
+		jsonData, err := json.Marshal(body)
+		if err != nil {
+			return fmt.Errorf("failed to marshal request body: %w", err)
+		}
+		reqBody = bytes.NewBuffer(jsonData)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", u, reqBody)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.config.AccessToken)
+	if body != nil {
+		req.Header.Set("Content-Type", "application/json")
+	}
+
+	return c.executeRequest(req, result)
+}
+
+// graphAPIPostForm performs an authenticated POST with multipart form fields.
+func (c *Client) graphAPIPostForm(ctx context.Context, path string, fields map[string]string, result any) error {
+	u := fmt.Sprintf("https://graph.facebook.com/%s/%s", c.config.APIVersion, path)
+
+	var buf bytes.Buffer
+	writer := multipart.NewWriter(&buf)
+	for k, v := range fields {
+		if err := writer.WriteField(k, v); err != nil {
+			return fmt.Errorf("failed to write form field %s: %w", k, err)
+		}
+	}
+	if err := writer.Close(); err != nil {
+		return fmt.Errorf("failed to close multipart writer: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "POST", u, &buf)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.config.AccessToken)
+	req.Header.Set("Content-Type", writer.FormDataContentType())
+
+	return c.executeRequest(req, result)
+}
+
+// graphAPIDelete performs an authenticated DELETE request.
+func (c *Client) graphAPIDelete(ctx context.Context, path string, params url.Values) error {
+	u := fmt.Sprintf("https://graph.facebook.com/%s/%s", c.config.APIVersion, path)
+	if len(params) > 0 {
+		u += "?" + params.Encode()
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "DELETE", u, nil)
+	if err != nil {
+		return fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.config.AccessToken)
+
+	return c.executeRequest(req, nil)
+}
+
+// executeRequest runs an HTTP request, handles error responses, and optionally unmarshals the body.
+func (c *Client) executeRequest(req *http.Request, result any) error {
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return fmt.Errorf("request failed: %w", err)
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
+		var errResp ErrorResponse
+		if err := json.Unmarshal(body, &errResp); err == nil && errResp.Error.Message != "" {
+			return fmt.Errorf("API error: %s (code: %d)", errResp.Error.Message, errResp.Error.Code)
+		}
+		return fmt.Errorf("API returned status %d: %s", resp.StatusCode, string(body))
+	}
+
+	if result != nil && len(body) > 0 {
+		if err := json.Unmarshal(body, result); err != nil {
+			return fmt.Errorf("failed to parse response: %w", err)
+		}
+	}
+	return nil
+}
+
+// postToMessagesEndpoint POSTs an arbitrary body to the phone number's /messages endpoint.
+// Used by sendMessage (typed) and by reaction/read-receipt (different top-level shape).
+func (c *Client) postToMessagesEndpoint(ctx context.Context, body any) (string, error) {
+	path := c.config.PhoneNumberID + "/messages"
+
+	jsonData, err := json.Marshal(body)
+	if err != nil {
+		return "", fmt.Errorf("failed to marshal message: %w", err)
+	}
+
+	u := fmt.Sprintf("https://graph.facebook.com/%s/%s", c.config.APIVersion, path)
+	req, err := http.NewRequestWithContext(ctx, "POST", u, bytes.NewBuffer(jsonData))
+	if err != nil {
+		return "", fmt.Errorf("failed to create request: %w", err)
+	}
+	req.Header.Set("Authorization", "Bearer "+c.config.AccessToken)
+	req.Header.Set("Content-Type", "application/json")
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return "", fmt.Errorf("failed to send request: %w", err)
+	}
+	defer resp.Body.Close()
+
+	respBody, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("failed to read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		var errResp ErrorResponse
+		if err := json.Unmarshal(respBody, &errResp); err == nil {
+			return "", fmt.Errorf("API error: %s (code: %d)", errResp.Error.Message, errResp.Error.Code)
+		}
+		return "", fmt.Errorf("API returned status %d: %s", resp.StatusCode, string(respBody))
+	}
+
+	var sendResp SendMessageResponse
+	if err := json.Unmarshal(respBody, &sendResp); err != nil {
+		return "", nil // some endpoints (read receipt) return non-message JSON
+	}
+	if len(sendResp.Messages) == 0 {
+		return "", nil
+	}
+	return sendResp.Messages[0].ID, nil
+}