Make kinship optional

sdk-scrapper/src/main/kotlin/io/github/wulkanowy/sdk/scrapper/student/StudentGuardian.kt

@@ -16,7 +16,7 @@ data class StudentGuardian(
     val lastName: String,
 
     @Json(name = "StPokrewienstwa")
-    val kinship: String,
+    val kinship: String?,
 
     @Json(name = "Adres")
     val address: String,

sdk/src/main/kotlin/io/github/wulkanowy/sdk/mapper/StudentMapper.kt

@@ -36,6 +36,6 @@ private fun ScrapperStudentGuardian.toFamilyMember() = StudentGuardian(
     fullName = fullName,
     email = email.orEmpty(),
     address = address,
-    kinship = kinship,
+    kinship = kinship.orEmpty(),
     phones = phone
 )