feat: Add template display name (backend) (#4966)

* Rename to nameValidator

* Refactor: NameValid

* Fix: comment

* Define new migration

* Include display_name

* Update typesGenerated.ts

* Update meta

* Adjust tests

* CLI tests

* Fix: audit

* Fix: omitempty

* site: display_name is optional

* unit: TestUsernameValid

* entities.ts: add display_name

* site: TemplateSettingsPage.test.tsx

* Fix: TemplateSettingsForm.tsx

* Adjust tests

* Add comment to display_name column

* Fix: rename

* Fix: make

* Loosen regexp

* Fix: err check

* Fix: template name length

* Allow for whitespaces

* Update migration number

coderd/database/models.go

@@ -589,6 +589,8 @@ type Template struct {
 	Icon       string      `db:"icon" json:"icon"`
 	UserACL    TemplateACL `db:"user_acl" json:"user_acl"`
 	GroupACL   TemplateACL `db:"group_acl" json:"group_acl"`
+	// Display name is a custom, human-friendly template name that user can set.
+	DisplayName string `db:"display_name" json:"display_name"`
 }
 
 type TemplateVersion struct {