rework convert button logic

src/main/resources/fxml/convertvault_hubtolocal_convert.fxml

@@ -1,10 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
+<?import org.cryptomator.ui.controls.FontAwesome5Spinner?>
 <?import javafx.geometry.Insets?>
+<?import javafx.scene.control.Button?>
+<?import javafx.scene.control.ButtonBar?>
 <?import javafx.scene.layout.Region?>
 <?import javafx.scene.layout.VBox?>
-<?import javafx.scene.control.ButtonBar?>
-<?import javafx.scene.control.Button?>
 <VBox xmlns:fx="http://javafx.com/fxml"
 	  xmlns="http://javafx.com/javafx"
 	  fx:controller="org.cryptomator.ui.convertvault.HubToLocalConvertController"
@@ -25,7 +26,11 @@
 			<ButtonBar buttonMinWidth="120" buttonOrder="+CI">
 				<buttons>
 					<Button text="%generic.button.cancel" ButtonBar.buttonData="CANCEL_CLOSE" cancelButton="true" onAction="#close"/>
-					<Button text="%convertVault.convert.convertBtn" ButtonBar.buttonData="FINISH" defaultButton="true" onAction="#convert" disable="${!controller.newPasswordController.goodPassword}"/>
+					<Button fx:id="convertBtn" ButtonBar.buttonData="FINISH" defaultButton="true" onAction="#convert"> <!-- for button logic, see controller -->
+						<graphic>
+							<FontAwesome5Spinner glyphSize="12"/>
+						</graphic>
+					</Button>
 				</buttons>
 			</ButtonBar>
 		</VBox>

src/main/resources/i18n/strings.properties

@@ -462,7 +462,8 @@ recoveryKey.recover.resetSuccess.description=You can unlock your vault with the
 
 # Convert Vault
 convertVault.title=Convert vault
-convertVault.convert.convertBtn=Convert vault
+convertVault.convert.convertBtn.before=Convert vault
+convertVault.convert.convertBtn.processing=Converting…
 convertVault.success.message=Conversion successful
 convertVault.success.description=You can now unlock the vault with the chosen password without requiring authentication or internet access.