feat: 토큰 생성, 검증, 조회 구현

- JWT 생성 구현
- Claims(Payload), 검증, 조회 미구현

resolve : #27

src/main/java/univ/goormthon/kongju/global/jwt/provider/JwtProvider.java

@@ -0,0 +1,38 @@
+package univ.goormthon.kongju.global.jwt.provider;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jwts;
+import org.springframework.security.core.Authentication;
+import org.springframework.stereotype.Component;
+
+import javax.crypto.SecretKey;
+import java.util.Date;
+
+@Component
+public class JwtProvider {
+
+    private final SecretKey key = Jwts.SIG.HS256.key().build();
+    private final long validityInMilliseconds = 1000 * 60 * 60; // 1시간
+
+    public String generateToken(Authentication authentication) {
+        String email = authentication.getName();
+
+        return Jwts.builder()
+                .subject(email)
+                .signWith(key)
+                .issuedAt(new Date())
+                .expiration(new Date(new Date().getTime() + validityInMilliseconds))
+                .compact();
+    }
+
+    public Claims getClaims(String token) {
+    }
+
+    public boolean validateToken(String token) {
+    }
+
+    public Authentication getAuthentication(String token) {
+    }
+
+
+}