[#70] feat(OldestCursor): 장르용 커서 추가

src/main/java/com/napzak/domain/genre/api/dto/request/cursor/OldestCursor.java

@@ -0,0 +1,45 @@
+package com.napzak.domain.genre.api.dto.request.cursor;
+
+import com.napzak.global.common.exception.NapzakException;
+import com.napzak.global.common.exception.code.ErrorCode;
+
+public class OldestCursor {
+	private final Long id;
+
+	public OldestCursor(Long id) {
+		this.id = id;
+	}
+
+	public Long getId() {
+		return id;
+	}
+
+	// O-{id}
+	@Override
+	public String toString() {
+		final StringBuilder stringBuilder = new StringBuilder();
+		return stringBuilder
+			.append("O-")
+			.append(id)
+			.toString();
+	}
+
+	public static OldestCursor fromString(String cursor) {
+		if (!cursor.startsWith("O-")) {
+			throw new NapzakException(ErrorCode.INVALID_CURSOR_FORMAT);
+		}
+		String[] split = cursor.split("-");
+
+		if (split.length != 2) {
+			throw new NapzakException(ErrorCode.INVALID_CURSOR_FORMAT);
+		}
+		final long id;
+
+		try{
+			id = Long.parseLong(split[1]);
+		} catch (NumberFormatException e) {
+			throw new NapzakException(ErrorCode.INVALID_CURSOR_FORMAT);
+		}
+		return new OldestCursor(id);
+	}
+}