ModelAdmin summary and view only (Scafolding)

Questions
1

Silverstripe Version: 4*

The form default options are summary, add and edit views. I would like to show “view” instead of edit form. I’m using this for a newsletter and once the mail is sent and the copy is saved in DB it should not be edited.

class NewsLetter extends DataObject {
private static $db = [
        'Subject' => 'Varchar',
        'Content' => 'HTMLText'
    ];

    private static $summary_fields = [
        'ID',
        'Subject',
        'Content.Plain' => 'Content',
        'Created' => 'Sent',
        'GroupNames' => 'Groups' 
    ];

    private static $many_many  = [
        'Group' => Group::class,
    ];
2

You can modify the edit permissions by implementing a canEdit() method in the class. I recommend checking out the model-level permissions documentation.