refactor: 로그 마스킹에서 맨 앞, 맨 뒤 글자는 표시하도록 수정

src/main/kotlin/roomescape/common/log/RoomescapeLogMaskingConverter.kt

@@ -11,10 +11,9 @@ import roomescape.common.config.JacksonConfig
 
 private const val MASK: String = "****"
 private val SENSITIVE_KEYS = setOf("password", "accessToken")
-
-class RoomescapeLogMaskingConverter(
 private val objectMapper: ObjectMapper = JacksonConfig().objectMapper()
-) : MessageConverter() {
+
+class RoomescapeLogMaskingConverter : MessageConverter() {
     override fun convert(event: ILoggingEvent): String {
         val message: String = event.formattedMessage
 
@@ -42,8 +41,17 @@ class RoomescapeLogMaskingConverter(
         return regex.replace(message) { matchResult ->
             val key = matchResult.groupValues[1]
             val delimiter = matchResult.groupValues[2]
+            val maskedValue = maskValue(matchResult.groupValues[3])
 
-            "${key}${delimiter}${MASK}"
+            "${key}${delimiter}${maskedValue}"
+        }
+    }
+
+    private fun maskValue(value: String): String {
+        return if (value.length <= 2) {
+            MASK
+        } else {
+            "${value.first()}$MASK${value.last()}"
         }
     }