Create rule S8304: Duplicate import statements should be removed

rules/S8304/groovy/metadata.json

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+{
+  "title": "Duplicate import statements should be removed",
+  "type": "CODE_SMELL",
+  "status": "ready",
+  "remediation": {
+    "func": "Constant/Issue",
+    "constantCost": "1 min"
+  },
+  "tags": [],
+  "defaultSeverity": "Critical",
+  "ruleSpecification": "RSPEC-8304",
+  "sqKey": "S8304",
+  "scope": "All",
+  "defaultQualityProfiles": [
+    "Sonar way"
+  ],
+  "quickfix": "unknown",
+  "code": {
+    "impacts": {
+      "MAINTAINABILITY": "HIGH"
+    },
+    "attribute": "CLEAR"
+  }
+}

rules/S8304/groovy/rule.adoc

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+This rule raises an issue when the same import statement appears multiple times in a Groovy file.
+
+== Why is this an issue?
+
+Duplicate import statements create unnecessary code clutter without providing any functional benefit.
+
+While duplicate imports don't cause compilation errors or runtime issues in Groovy, they make the code harder to read and maintain.
+
+Keeping import statements clean and minimal helps developers quickly understand the dependencies of a file and reduces visual noise in the codebase.
+
+=== What is the potential impact?
+
+This issue has minimal impact on functionality but affects code readability and maintainability. Clean import sections help developers understand file dependencies more quickly.
+
+== How to fix it
+
+Remove the duplicate import statement. Keep only one instance of each import.
+
+=== Code examples
+
+==== Noncompliant code example
+
+[source,groovy,diff-id=1,diff-type=noncompliant]
+----
+import java.util.List
+import java.util.Map
+import java.util.List // Noncompliant
+----
+
+==== Compliant solution
+
+[source,groovy,diff-id=1,diff-type=compliant]
+----
+import java.util.List
+import java.util.Map
+----

rules/S8304/metadata.json

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+{
+}