fix: allow login by email case-insensitive (#7578)

A customer noted that the login by email was case-sensitive, which differs to the handling of the loginname.

This PR changes the email check to be case-insensitive (which it was already in same parts) and improve the search for this as well.

cmd/setup/25.go

@@ -0,0 +1,27 @@
+package setup
+
+import (
+	"context"
+	_ "embed"
+
+	"github.com/zitadel/zitadel/internal/database"
+	"github.com/zitadel/zitadel/internal/eventstore"
+)
+
+var (
+	//go:embed 25.sql
+	addLowerFieldsToVerifiedEmail string
+)
+
+type AddLowerFieldsToVerifiedEmail struct {
+	dbClient *database.DB
+}
+
+func (mig *AddLowerFieldsToVerifiedEmail) Execute(ctx context.Context, _ eventstore.Event) error {
+	_, err := mig.dbClient.ExecContext(ctx, addLowerFieldsToVerifiedEmail)
+	return err
+}
+
+func (mig *AddLowerFieldsToVerifiedEmail) String() string {
+	return "25_add_lower_fields_to_verified_email"
+}