Create Initial Database Schema for Tasks. (#1)

Create migration scripts for this and initial Task DB Model in rust along with unit tests.

Reviewed-on: #1
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

backend/src/models/mod.rs

@@ -0,0 +1,3 @@
+mod task;
+
+pub use task::*;