[Hard] Implement /token endpoint

[keepsloading]

Exchange authorization codes for short-lived access tokens and refresh tokens.

[keepsloading]

Friendly reminder for SSoC26 contributors: When you submit a Pull Request for this issue, please remember to also raise a dummy PR in the Memact/Context repository that references your original PR. This is required for your contribution to be considered for points on the SSoC leaderboard!

[Archita-29]

hey @keepsloading!! Assign it to me.