This commit adds a new API `POST /api/tx` that sends an ad-hoc message
to a subscriber based on a pre-defined transactional template. This is
a large commit that adds the following:
- New campaign / tx template types on the UI. tx templates have an
additional subject field.
- New fields `type` and `subject` to the templates table.
- Refactor template CRUD operations and models.
- Refactor template func assignment in manager.
- Add pre-compiled template caching to manager runtime.
- Pre-compile all tx templates into memory on program boot to avoid
expensive template compilation on ad-hoc tx messages.
- Refactor codeflask HTML editor into a standalone html-editor
component.
- Replace the plaintext box in the template editor with html-editor.
- Replace codeflask in the campaign editor with the new html-editor.
- Refactor templates Cypress tests to test the new editor.
- Refactor campaigns Cypress tests to test the new editor and also
test switching between different editors and content formats.
The default `{{ TrackLink "https://listmonk.app" }}` template function
is clumsy to write and does breaks WYSIWYG editors and HTML syntax
highlighting because of the quotes. The new syntax doesn't break HTML
and is easier to write.
Eg: `<a href="https://listmonk.app@TrackLink">Link</a>`
- Introduce @TrackLink shorthand.
- Add first-class support for tracking links in the WYSIWYG (TinyMCE)
editor by introducing an on/off checkbox on the link dialog.
- Improve default dummy campaign content to highlight this.
- Change public and admin frontend primary colours.
- Change images.
- Refactor and fix styling on public pages.
- Remove CSS grid lib from public pages.
- Update Buefy and fix broken component styles (modal, toast).
