[FEATURE] Add registration form for abandoned extensions

extensions/ter_fe2/Resources/Private/Forms/abandon-extension.form.yaml

+
+renderingOptions:
+  submitButtonLabel: Submit
+type: Form
+identifier: abandon-extension
+label: abandon-extension
+prototypeName: standard
+finishers:
+  -
+    options:
+      subject: 'maintain extension'
+      recipientAddress: maintenance@typo3.org
+      recipientName: 'typo3.org maintenance team'
+      senderAddress: info@typo3.org
+      senderName: 'typo3.org website'
+      replyToAddress: ''
+      carbonCopyAddress: ''
+      blindCarbonCopyAddress: ''
+      format: html
+      attachUploads: true
+      translation:
+        language: ''
+    identifier: EmailToReceiver
+renderables:
+  -
+    renderingOptions:
+      previousButtonLabel: 'Previous step'
+      nextButtonLabel: 'Next step'
+    type: Page
+    identifier: page-1
+    label: Step
+    renderables:
+      -
+        defaultValue: ''
+        type: Text
+        identifier: text-1
+        label: Name
+        properties:
+          fluidAdditionalAttributes:
+            required: required
+        validators:
+          -
+            identifier: NotEmpty
+      -
+        defaultValue: ''
+        type: Text
+        identifier: text-2
+        label: Mail
+        properties:
+          fluidAdditionalAttributes:
+            required: required
+        validators:
+          -
+            identifier: NotEmpty
+          -
+            identifier: EmailAddress
+      -
+        defaultValue: ''
+        type: Text
+        identifier: text-3
+        label: 'Extension Key'
+        properties:
+          fluidAdditionalAttributes:
+            required: required
+          elementDescription: 'Tell us, which extension key you like to maintain'
+        validators:
+          -
+            identifier: NotEmpty
+      -
+        defaultValue: ''
+        type: Textarea
+        identifier: textarea-1
+        label: Message
+        properties:
+          elementDescription: ''

extensions/ter_fe2/Resources/Private/Templates/Extension/Show.html

@@ -51,8 +51,8 @@
                 <div class="alert alert-danger mt-3 mb-3" role="alert">
                     <h4 class="alert-header">
                         <span class="ter-ext-state-beta"><i class="fa fa-exclamation-triangle"></i></span>
-                        Obsolete extension
-                        <small class="text-muted">This extension is marked as obsolete and not supported anymore</small>
+                        Abandoned extension
+                        <small class="text-muted">This extension has no maintainer at the moment. If you like to get the maintainer of this extension, fill out our <f:link.page pageUid="408">registration form</f:link.page>.</small>
                     </h4>
                 </div>
             </f:if>