feat : Get Tags Controller, Service, Repository Implement.

src/main/java/com/io/realworld/domain/aggregate/tag/controller/TagController.java

@@ -0,0 +1,26 @@
+package com.io.realworld.domain.aggregate.tag.controller;
+
+import com.io.realworld.domain.aggregate.tag.dto.TagResponse;
+import com.io.realworld.domain.aggregate.tag.service.TagService;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/tags")
+public class TagController {
+
+    private final TagService tagService;
+
+    public TagController(TagService tagService) {
+        this.tagService = tagService;
+    }
+
+    //Todo Response tags: {} ~
+    @GetMapping
+    public List<String> getTags(){
+        return tagService.getTags();
+    }
+}

src/main/java/com/io/realworld/domain/aggregate/tag/service/TagService.java

@@ -11,4 +11,5 @@ import java.util.List;
 
 public interface TagService {
     void save(Article article);
+    List<String> getTags();
 }

src/main/java/com/io/realworld/domain/aggregate/tag/service/TagServiceImpl.java

@@ -26,4 +26,9 @@ public class TagServiceImpl implements TagService {
             tagRepository.save(tag);
         }
     }
+
+    @Override
+    public List<String> getTags() {
+        return tagRepository.findAll().stream().map(Tag::getTagName).distinct().collect(Collectors.toList());
+    }
 }