Squashed commit of the following:

commit d2ec8c0f07
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Thu May 15 15:42:33 2025 +0700

    add: db tx commit and rollback implementation

commit 264435f67e
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Thu May 15 14:34:20 2025 +0700

    fix: shortlink generation logic update/create

commit 047ab1937a
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Thu May 15 11:06:04 2025 +0700

    fix: if multiple studies patient, show first study by default

commit c13f834b92
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Thu May 15 09:46:32 2025 +0700

    add: register and login with DB query AND some struct type correction

commit dd4451c2a8
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Wed May 14 10:23:33 2025 +0700

    new file structure & koneksi ke DB

commit 8289881df3
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 16:49:07 2025 +0700

    edit: rm debug route

commit dd784da232
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 15:44:11 2025 +0700

    add: implement shortlink

commit 2687a761cc
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 11:47:19 2025 +0700

    add new dummy doctor user

commit eb67eaca46
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 11:46:28 2025 +0700

    add: ref_doctor studylist filter

commit 0d4825d152
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 10:07:16 2025 +0700

    edit study_iuids & accNum in patient jwt to array

commit 2d1f135fda
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Tue May 13 09:52:45 2025 +0700

    patient see their multiple studies

commit 13bb380f51
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Fri May 9 10:13:16 2025 +0700

    add: cors handler route and readme

commit 6c9ab574ce
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Mon May 5 11:50:36 2025 +0700

    add: login & token validation tapi belum connect ke DB

commit 297c9a6a01
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Mon Apr 28 15:37:02 2025 +0700

    add readme.md

commit 9b8e0260f3
Author: mario <dev.mario@sismedika@gmail.com>
Date:   Mon Apr 7 15:46:07 2025 +0700

    connected-to-google

commit f340bc5916
Author: mario <dev.mario@sismedika.com>
Date:   Mon Apr 7 11:14:18 2025 +0700

    init

internal/auth/google.go

@@ -0,0 +1,68 @@
+package auth
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"time"
+
+	"golang.org/x/oauth2"
+	"golang.org/x/oauth2/google"
+	"google.golang.org/api/healthcare/v1"
+	"google.golang.org/api/option"
+)
+
+// GoogleClient handles authentication with Google APIs
+type GoogleClient struct {
+	credentialsPath string
+	tokenSource     oauth2.TokenSource
+}
+
+// NewGoogleClient creates a new Google authentication client
+func NewGoogleClient(credentialsPath string) (*GoogleClient, error) {
+	client := &GoogleClient{
+		credentialsPath: credentialsPath,
+	}
+
+	// Initialize on creation to validate credentials
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	// Try reading the credentials file
+	credBytes, err := os.ReadFile(credentialsPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read credentials file: %w", err)
+	}
+
+	// Create credentials from the JSON key file
+	creds, err := google.CredentialsFromJSON(ctx, credBytes, healthcare.CloudPlatformScope)
+	if err != nil {
+		return nil, fmt.Errorf("failed to initialize Google client: %w", err)
+	}
+
+	client.tokenSource = creds.TokenSource
+	return client, nil
+}
+
+// GetAccessToken returns a valid access token for Google APIs
+func (c *GoogleClient) GetAccessToken() (string, error) {
+	_, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	token, err := c.tokenSource.Token()
+	if err != nil {
+		return "", fmt.Errorf("failed to get access token: %w", err)
+	}
+
+	return token.AccessToken, nil
+}
+
+// GetHealthcareClient returns a configured Healthcare API client
+func (c *GoogleClient) GetHealthcareClient(ctx context.Context) (*healthcare.Service, error) {
+	opts := []option.ClientOption{
+		option.WithCredentialsFile(c.credentialsPath),
+		option.WithScopes(healthcare.CloudPlatformScope),
+	}
+
+	return healthcare.NewService(ctx, opts...)
+}