Refactor domain models (DomFunktionaer, DomReiter, DomPferd) for ZNS alignment: update properties, streamline validation logic, and enhance parser to support new format. Adjust controllers and repository methods accordingly.

core/core-utils/src/commonMain/kotlin/at/mocode/core/utils/parser/FixedWidthParser.kt

@@ -1,5 +1,7 @@
 package at.mocode.core.utils.parser
 
+import kotlinx.datetime.LocalDate
+
 /**
  * A simple utility to parse fixed-width strings based on 1-based start positions and lengths.
  * This is particularly useful for parsing legacy data formats like the OePS ZNS formats.
@@ -36,4 +38,26 @@ class FixedWidthLineReader(private val line: String) {
     val str = getString(start1Based, length)
     return str.toIntOrNull()
   }
+
+  /**
+   * Extracts a string and parses it as a LocalDate (format YYYYMMDD).
+   * Returns null if the field is empty or cannot be parsed.
+   */
+  fun getLocalDateOrNull(start1Based: Int, length: Int): LocalDate? {
+    val str = getString(start1Based, length)
+    if (str.length != 8) return null
+
+    val year = str.substring(0, 4).toIntOrNull()
+    val month = str.substring(4, 6).toIntOrNull()
+    val day = str.substring(6, 8).toIntOrNull()
+
+    if (year == null || month == null || day == null) return null
+    if (month !in 1..12 || day !in 1..31) return null
+
+    return try {
+      LocalDate(year, month, day)
+    } catch (e: Exception) {
+      null
+    }
+  }
 }