Implement an Outbox for Emails

[Gagan-Ram]

fixes: #658

Summary by Sourcery

Implement an email outbox system in the sendmail plugin by queuing emails in the database instead of sending them immediately.

New Features:

• Introduce a QueuedMail model to persist outgoing emails with metadata and attachments.
• Queue emails in the SenderView rather than dispatching them immediately via a background task.
• Add outbox management views and templates to list, send (all or individual), delete, and purge queued emails.
• Register new URLs and navigation entries for the outbox interface.

Enhancements:

• Switch to get_email_context for placeholder resolution when queuing emails.
• Support customizable ordering in the outbox list view.

[sourcery-ai]

Reviewer's Guide

This PR replaces immediate asynchronous email dispatch with a persistent outbox queue: it introduces a QueuedMail model, enqueues messages per order and attendee using the new model, and adds outbox management views, URLs, templates, and navigation to review, send, or purge queued mails.

Sequence diagram for email queuing in the new outbox flow

sequenceDiagram
    actor Admin
    participant SenderView
    participant QueuedMail
    participant DB as Database

    Admin->>SenderView: Submit email form
    SenderView->>QueuedMail: Create QueuedMail for each recipient
    QueuedMail->>DB: Save QueuedMail instance(s)
    SenderView-->>Admin: Show success message

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Sequence diagram for sending all queued emails from the outbox

sequenceDiagram
    actor Admin
    participant OutboxListView
    participant QueuedMail
    participant DB as Database

    Admin->>OutboxListView: Click 'Send all' button
    OutboxListView->>QueuedMail: Fetch unsent mails
    loop For each unsent mail
        OutboxListView->>QueuedMail: send()
        QueuedMail->>DB: Update sent, sent_at
    end
    OutboxListView-->>Admin: Show result message

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ER diagram for QueuedMail and related entities

erDiagram
    QUEUEDMAIL ||--o{ EVENT : event
    QUEUEDMAIL }o--|| USER : user
    QUEUEDMAIL ||--o{ ORDER : order
    QUEUEDMAIL }o--|| ORDERPOSITION : position

    QUEUEDMAIL {
        bigint id PK
        varchar recipient
        text subject
        text message
        varchar reply_to
        text bcc
        varchar locale
        json attachments
        datetime created
        boolean sent
        datetime sent_at
    }

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Class diagram for the new QueuedMail model

classDiagram
    class QueuedMail {
        +Event event
        +User user
        +Order order
        +OrderPosition position
        +str recipient
        +str subject
        +str message
        +str reply_to
        +str bcc
        +str locale
        +JSON attachments
        +datetime created
        +bool sent
        +datetime sent_at
        +make_text(signature)
        +send(event_signature)
    }
    QueuedMail --> Event
    QueuedMail --> User
    QueuedMail --> Order
    QueuedMail --> OrderPosition

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File-Level Changes

Change	Details	Files
Refactor email sending to queue instead of immediate dispatch	Removed send_mails.apply_async call Looped over orders and attendees to create QueuedMail instances Switched to get_email_context for placeholder rendering Commented-out original log_action call	src/pretix/plugins/sendmail/views.py
Introduce QueuedMail model and migration	Added QueuedMail fields (recipient, subject, message, metadata) Implemented make_text and send() methods with exception handling Created initial Django migration for QueuedMail table	src/pretix/plugins/sendmail/models.py src/pretix/plugins/sendmail/migrations/0001_initial.py
Add outbox management views	OutboxListView with pagination and ordering SendAllQueuedMailsView to dispatch all unsent mails SendQueuedMailView for single-mail send DeleteQueuedMailView and PurgeQueuedMailsView for discarding mails	src/pretix/plugins/sendmail/views.py
Register outbox routes	Added URL patterns for outbox list, send all, send single, delete, and purge actions	src/pretix/plugins/sendmail/urls.py
Provide outbox UI template	Created outbox_list.html showing queued mails with action buttons Included pagination and batch send/purge forms	src/pretix/plugins/sendmail/templates/pretixplugins/sendmail/outbox_list.html
Add navigation entry for Outbox	Inserted 'Outbox' child link in control_nav_import signal Set active state based on URL namespace and name	src/pretix/plugins/sendmail/signals.py

Possibly linked issues

• Implement an Outbox for Emails #658: The PR implements the outbox feature by adding a QueuedMail model and views to manage queued emails.

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[mariobehling]

Thanks for this draft. Please ensure the following works as well:

• Align buttons next to each other or in the same way as existing styles
• Fix button texts, e.g. "Send to Outbox" instead of "Send"
• Fix -all- relevant helper texts, e.g. "Your email has been sent to the outbox." instead of "Your email will be sent...", "Your email has been sent." etc.
• Add option: Do you really want to delete this mail?
• Please test and document that the feature works with a larger number of attendees/recipients.
• Include the helper text below the text fields same as on the original email compose form.
• Attachment option is missing in email edit form.

[Gagan-Ram]

@mariobehling Could you please clarify/elaborate more on the below:

• Align buttons next to each other or in the same way as existing styles
• Include the helper text below the text fields same as on the original email compose form.

[mariobehling]

Below are two examples. Please check all button implementations and ensure they follow existing styles and placements on the platform.

[hpdang]

@Gagan-Ram how about the handling multiple receivers? Is it going to be done today too?

[hpdang]

@Gagan-Ram I saw you opened a new PR for multiple receivers. Why is it still in draft mode?

[Gagan-Ram]

@hpdang Sorry I didn't notice your message, maybe it was cleared from my notification when I was clearing stale ones.
The PR was in draft mode because of the mail system bug I was talking about last week. However the PR is now working as you have requested.

[Gagan-Ram]

I am closing this PR as the newer PR #780 is more aligned with the changes requested by maintainers.
Thank you