fix: simplify how filters are built

Author: jwilkinson87

src/main/kotlin/com/ctrlhub/core/router/request/FilterExpression.kt

@@ -11,19 +11,8 @@ class FieldFilterExpression(val field: String, val values: List<String>) : Filte
     }
 }
 
-class ValueFilterExpression(val values: List<String>) : FilterOption {
-    override fun format(): String = values.joinToString(",")
-}
-
-class FunctionFilterExpression(val name: String, val args: List<String> = emptyList()) : FilterOption {
-    override fun format(): String {
-        return if (args.isEmpty()) {
-            "${name}()"
-        } else {
-            val joined = args.joinToString(",") { it }
-            "${name}(${joined})"
-        }
-    }
+class ValueFilterExpression(val value: String) : FilterOption {
+    override fun format(): String = value
 }
 
 class AndExpression(val parts: List<FilterOption>) : FilterOption {

src/test/kotlin/com/ctrlhub/core/router/request/RequestParametersFiltersTest.kt

@@ -24,12 +24,8 @@ class RequestParametersFiltersTest {
     fun `and of functions formats correctly`() {
         val expr = AndExpression(
             listOf(
-                ValueFilterExpression(
-                    listOf(
-                        "is_latest()",
-                        "no_start()"
-                    )
-                ),
+                ValueFilterExpression("is_latest()"),
+                ValueFilterExpression("no_start()"),
             )
         )
 
@@ -44,7 +40,7 @@ class RequestParametersFiltersTest {
         val expr = AndExpression(
             listOf(
                 FieldFilterExpression("status", listOf("active")),
-                FunctionFilterExpression("is_latest")
+                ValueFilterExpression("is_latest()")
             )
         )