ci: add dart_code_metrics rules

analysis_options.yaml

@@ -28,3 +28,22 @@ include: package:lints/recommended.yaml
 
 # For additional information about configuring this file, see
 # https://dart.dev/guides/language/analysis-options
+
+dart_code_metrics:
+  anti-patterns:
+    - long-method
+    - long-parameter-list
+  metrics:
+    cyclomatic-complexity: 20
+    maximum-nesting-level: 5
+    number-of-parameters: 4
+    source-lines-of-code: 50
+  metrics-exclude:
+    - test/**
+  rules:
+    - newline-before-return
+    - no-boolean-literal-compare
+    - no-empty-block
+    - prefer-trailing-comma
+    - prefer-conditional-expressions
+    - no-equal-then-else