Trigger certificate chooser on authentication change

If the user chooses client certificate authentication,
immediately pop up the certificate chooser.

If the user chooses password authentication, move the focus to the
password View.

src/com/fsck/k9/activity/setup/AccountSetupIncoming.java

@@ -323,6 +323,16 @@ public class AccountSetupIncoming extends K9Activity implements OnClickListener
                     long id) {
                 updateViewFromAuthType();
                 validateFields();
+                AuthType selection = (AuthType) mAuthTypeView.getSelectedItem();
+
+                // Have the user select (or confirm) the client certificate
+                if (AuthType.EXTERNAL.equals(selection)) {
+
+                    // This may again invoke validateFields()
+                    mClientCertificateSpinner.chooseCertificate();
+                } else {
+                    mPasswordView.requestFocus();
+                }
             }
 
             @Override

src/com/fsck/k9/activity/setup/AccountSetupOutgoing.java

@@ -223,6 +223,16 @@ public class AccountSetupOutgoing extends K9Activity implements OnClickListener,
                     long id) {
                 updateViewFromAuthType();
                 validateFields();
+                AuthType selection = (AuthType) mAuthTypeView.getSelectedItem();
+
+                // Have the user select (or confirm) the client certificate
+                if (AuthType.EXTERNAL.equals(selection)) {
+
+                    // This may again invoke validateFields()
+                    mClientCertificateSpinner.chooseCertificate();
+                } else {
+                    mPasswordView.requestFocus();
+                }
             }
 
             @Override

src/com/fsck/k9/view/ClientCertificateSpinner.java

@@ -51,7 +51,7 @@ public class ClientCertificateSpinner extends LinearLayout {
         mSelection.setOnClickListener(new OnClickListener() {
             @Override
             public void onClick(View v) {
-                onSelect();
+                chooseCertificate();
             }
         });
 
@@ -96,7 +96,7 @@ public class ClientCertificateSpinner extends LinearLayout {
         setAlias(null);
     }
 
-    private void onSelect() {
+    public void chooseCertificate() {
         // NOTE: keyTypes, issuers, hosts, port are not known before we actually
         // open a connection, thus we cannot set them here!
         KeyChain.choosePrivateKeyAlias(mActivity, new KeyChainAliasCallback() {