fix(gcp): detect credential type before requesting token source

Switch from CredentialsFromJSONWithParams to CredentialsFromJSONWithType to properly handle different GCP credential formats. Add credential type detection helper to parse the JSON and extract the credential type field.

Author: moshloop

connection/gcp.go

@@ -1,6 +1,7 @@
 package connection
 
 import (
+	"encoding/json"
 	"fmt"
 	"strings"
 	"time"
@@ -45,14 +46,32 @@ func (t *GCPConnection) FromModel(connection models.Connection) {
 }
 
 func (g *GCPConnection) TokenSource(ctx context.Context, scopes ...string) (oauth2.TokenSource, error) {
-	creds, err := google.CredentialsFromJSONWithParams(ctx, []byte(g.Credentials.ValueStatic), google.CredentialsParams{Scopes: scopes})
+	credType, err := detectCredentialType([]byte(g.Credentials.ValueStatic))
+	if err != nil {
+		return nil, fmt.Errorf("detecting credential type: %w", err)
+	}
+
+	creds, err := google.CredentialsFromJSONWithType(ctx, []byte(g.Credentials.ValueStatic), credType, scopes...)
 	if err != nil {
 		return nil, err
 	}
 
 	return creds.TokenSource, nil
 }
 
+func detectCredentialType(jsonData []byte) (google.CredentialsType, error) {
+	var f struct {
+		Type string `json:"type"`
+	}
+	if err := json.Unmarshal(jsonData, &f); err != nil {
+		return "", fmt.Errorf("parsing credentials JSON: %w", err)
+	}
+	if f.Type == "" {
+		return google.ServiceAccount, nil
+	}
+	return google.CredentialsType(f.Type), nil
+}
+
 func (g *GCPConnection) Validate() *GCPConnection {
 	if g == nil {
 		return &GCPConnection{}