Feat(Backend): Enable search post by text

[ryanycw]

Describe the solution you'd like

• Refactor the current get post route to allow passing keywords as query params
  

  social-tw-website/packages/relay/src/routes/postRoute.ts

  Line 18 in 9cc927d

  '/api/post',

• And in fetchPosts search for content that contain keywords
  

  social-tw-website/packages/relay/src/services/PostService.ts

  Line 143 in 9cc927d

  async fetchPosts(

  if (keywords) {
      whereClause.content = { contains: keywords }
  }
  

• Add test in post.test for fetchPosts with keyword
  https://github.com/social-tw/social-tw-website/blob/main/packages/relay/test/post.test.ts