feat: KatchupDomain class 구현

Author: unanchoi

src/main/kotlin/site/katchup/springboot/global/KatchupDomain.kt

@@ -0,0 +1,7 @@
+package site.katchup.springboot.global
+
+class KatchupDomain {
+    companion object {
+        const val DOMAIN = ".katchup.kr"
+    }
+}