Add 18 community AL/BC patterns across style, data-modeling, web-services, appsource, breaking-changes, performance, and testing

Contributed by CURABIS ApS, generalized from patterns observed across real AppSource/PTE development. Each article follows the knowledge file format (frontmatter, Description/Best Practice/Anti Pattern, sibling .good.al/.bad.al samples).

microsoft/knowledge/breaking-changes/prefer-email-module.bad.al

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+codeunit 50103 "Order Confirmation Notifier"
+{
+    procedure Send(FromName: Text; ToAddress: Text; Subject: Text; Body: Text)
+    var
+        Mail: Codeunit Mail;
+        MailSent: Boolean;
+    begin
+        Mail.CreateMessage(FromName, ToAddress, '', Subject, Body, true);
+        MailSent := Mail.Send();
+        if not MailSent then
+            Message(Mail.GetErrorDesc());
+    end;
+}

microsoft/knowledge/breaking-changes/prefer-email-module.good.al

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+codeunit 50103 "Order Confirmation Notifier"
+{
+    procedure Send(ToAddress: Text; Subject: Text; Body: Text)
+    var
+        Email: Codeunit Email;
+        EmailMessage: Codeunit "Email Message";
+    begin
+        EmailMessage.Create(ToAddress, Subject, Body, true);
+        Email.Send(EmailMessage, Enum::"Email Scenario"::Default);
+    end;
+}

microsoft/knowledge/breaking-changes/prefer-email-module.md

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+---
+bc-version: [all]
+domain: breaking-changes
+keywords: [email, codeunit-mail, email-message, email-scenario, email-account, smtp, sending-email]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Send email through the Email module, not Codeunit Mail (397)
+
+> Contributions welcome — open a PR to refine or extend this article.
+
+## Description
+
+Older AL code sends email by calling `Codeunit Mail (397)`. Business Central's current extensibility model is a different, richer object set — `Codeunit Email`, table `Email Message`, `enum "Email Scenario"`, and the `Email Account`/`Email Connector` interface (Microsoft 365, Current User, SMTP, or a custom connector). New code built on `Codeunit Mail` inherits its SMTP-era, single-connector assumptions and leaves no Sent/Outbox trail behind.
+
+## Best Practice
+
+Build on `Codeunit Email` and table `Email Message`. Route the message through an `Email Scenario` so different document types can use different accounts without the calling code needing to know which account that is, and get a tracked Sent/Outbox/Draft record for free.
+
+See sample: `prefer-email-module.good.al`.
+
+## Anti Pattern
+
+Calling `Codeunit Mail`'s `CreateMessage`/`Send`/`GetErrorDesc`. It still runs, but it is hard-coupled to whatever SMTP setup exists, and leaves no queryable record of what was sent.
+
+See sample: `prefer-email-module.bad.al`.