feat: add following user infos in the following endpoint

[takanome-dev]

Description

This pr adds the following_user in the following endpoint response which is the following user's data.

What type of PR is this? (check all applicable)

• [x] 🍕 Feature
• [ ] 🐛 Bug Fix
• [ ] 📝 Documentation Update
• [ ] 🎨 Style
• [ ] 🧑‍💻 Code Refactor
• [ ] 🔥 Performance Improvements
• [ ] ✅ Test
• [ ] 🤖 Build
• [ ] 🔁 CI
• [ ] 📦 Chore (Release)
• [ ] ⏩ Revert

Related Tickets & Documents

Fixes #426

Mobile & Desktop Screenshots/Recordings

Added tests?

• [ ] 👍 yes
• [ ] 🙅 no, because they aren't needed
• [ ] 🙋 no, because I need help

Added to documentation?

• [ ] 📜 README.md
• [ ] 📓 docs.opensauced.pizza
• [ ] 🍕 dev.to/opensauced
• [ ] 📕 storybook
• [ ] 🙅 no documentation needed

[optional] Are there any post-deployment tasks we need to perform?

[optional] What gif best describes this PR or how it makes you feel?