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/style/var-parameters-require-an-addressable-variable.md

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+---
+bc-version: [all]
+domain: style
+keywords: [var-parameter, by-reference, pass-by-reference, literal, constant, compile-error, procedure-call]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# A `var` parameter must be called with a variable, never a literal or expression
+
+> Contributions welcome — open a PR to refine or extend this article.
+
+## Description
+
+When a procedure declares a parameter with `var`, that parameter is passed by reference: the callee writes back into the caller's own memory location. This means the argument at the call site must be an actual variable, something with an address. A string literal, a numeric constant, or a computed expression has no address to write back to, so passing one to a `var` parameter fails to compile. Before writing a call, check the callee's signature for `var` on each parameter position being supplied a literal or expression — if present, a variable declared in the caller's own scope must be used instead.
+
+## Best Practice
+
+Declare a variable in the caller's scope and pass it to the `var` parameter.
+
+See sample: `var-parameters-require-an-addressable-variable.good.al`.
+
+## Anti Pattern
+
+Passing a literal or a computed expression to a `var` parameter position fails to compile, because neither has an address the callee can write back to.
+
+See sample: `var-parameters-require-an-addressable-variable.bad.al`.