feat: Refactor user and thought models to use UUIDs instead of integers

- Updated user and thought models to utilize UUIDs for primary keys.
- Modified persistence functions to accommodate UUIDs for user and thought IDs.
- Implemented tag functionality with new Tag and ThoughtTag models.
- Added migration scripts to create new tables for tags and thought-tag relationships.
- Enhanced thought creation to parse hashtags and link them to thoughts.
- Updated tests to reflect changes in user and thought ID types.

thoughts-backend/models/src/schemas/user.rs

@@ -1,12 +1,13 @@
 use common::DateTimeWithTimeZoneWrapper;
 use serde::Serialize;
 use utoipa::ToSchema;
+use uuid::Uuid;
 
 use crate::domains::user;
 
 #[derive(Serialize, ToSchema)]
 pub struct UserSchema {
-    pub id: i32,
+    pub id: Uuid,
     pub username: String,
     pub display_name: Option<String>,
     pub bio: Option<String>,