feat : (#31) add googleOauthUserService

Author: qkrwndnjs1075

src/main/kotlin/entry/dsm/gitauth/equusgithubauth/global/oauth/service/GoogleOauthUserService.kt

@@ -0,0 +1,31 @@
+package entry.dsm.gitauth.equusgithubauth.global.oauth.service
+
+import entry.dsm.gitauth.equusgithubauth.domain.user.entity.User
+import entry.dsm.gitauth.equusgithubauth.domain.user.entity.enums.UserRole
+import entry.dsm.gitauth.equusgithubauth.domain.user.entity.repository.UserRepository
+import org.springframework.stereotype.Service
+
+@Service
+class GoogleOauthUserService(
+    private val userRepository: UserRepository
+) {
+    fun findOrCreateOAuthUser(
+        loginId: String,
+        email: String,
+        name: String,
+        provider: String,
+        providerId: String
+    ): User {
+        return userRepository.findByLoginId(loginId) ?: run {
+            User(
+                loginId = loginId,
+                email = email,
+                password = "",
+                name = name,
+                provider = provider,
+                providerId = providerId,
+                role = UserRole.USER
+            ).also { userRepository.save(it) }
+        }
+    }
+}