feat: Add scope, type, classifier, and optional properties to ArtifactDescriptor

Added new PomElement properties to ArtifactDescriptor for cleaner API:
- scope: dependency scope (compile, test, runtime, etc.)
- type: artifact type (jar, pom, etc.)
- classifier: artifact classifier (mule-plugin, sources, etc.)
- optional: whether dependency is optional (true/false)

All properties are PomElement for consistency with existing 'version' field:
- Tracks line numbers for violation reporting
- Handles property references like
- Provides null-safe access via ?. operator

Updated tests to use cleaner API:
- dependency.scope?.value instead of dependency.getAttribute('scope')?.value

All tests pass (including new PomManagementResolutionTest and full suite).

Author: adesjardin

mule-linter-core/src/test/groovy/com/avioconsulting/mule/linter/model/PomManagementResolutionTest.groovy

@@ -67,7 +67,7 @@ class PomManagementResolutionTest extends Specification {
         
         and: "Child-specific details (scope) are preserved"
         result.dependency != null
-        result.dependency.getAttribute('scope')?.value == "runtime"
+        result.dependency.scope?.value == "runtime"
         result.dependency.artifactId == "my-lib"
     }
 
@@ -83,6 +83,6 @@ class PomManagementResolutionTest extends Specification {
         result.version == "3.0.0"
         result.isVersionFromManagement == false
         result.versionSource == pomFile
-        result.dependency.getAttribute('scope')?.value == "compile"
+        result.dependency.scope?.value == "compile"
     }
 }

mule-linter-spi/src/main/groovy/com/avioconsulting/mule/linter/model/pom/ArtifactDescriptor.groovy

@@ -8,6 +8,10 @@ class ArtifactDescriptor {
     String groupId
     String artifactId
     PomElement version
+    PomElement scope
+    PomElement type
+    PomElement classifier
+    PomElement optional
     Integer lineNo
     PomFile pomFile
     GPathResult pluginXml
@@ -19,6 +23,10 @@ class ArtifactDescriptor {
         this.lineNo = getNodeLineNumber(pluginXml)
         this.pomFile = pomFile
         this.version = getAttribute('version')
+        this.scope = getAttribute('scope')
+        this.type = getAttribute('type')
+        this.classifier = getAttribute('classifier')
+        this.optional = getAttribute('optional')
     }
 
     PomElement getAttribute(String attributeName) {