[UST-229] [Backend] [Feat]: 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 https://github.com/social-tw/social-tw-website/blob/9cc927d0b2cebc0d550c3463265bc8dc16a0ee05/packages/relay/src/routes/postRoute.ts#L18

• And in fetchPosts search for content that contain keywords https://github.com/social-tw/social-tw-website/blob/9cc927d0b2cebc0d550c3463265bc8dc16a0ee05/packages/relay/src/services/PostService.ts#L143

  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

• Story Point: 3

• Reporter: @ryanycw

[Lisooo790926]

I think it's related to https://github.com/social-tw/social-tw-website/issues/520, I will wait for the reply then implement it. thanks