Added a new sync that uses hash

Added a new sync that uses hash and sqlc for the queries. Added db
migration. Started adding a config file.

sqlc.yaml

@@ -0,0 +1,37 @@
+version: "2"
+sql:
+  - engine: "postgresql"
+    queries: "./db/queries"
+    schema: "./db/migrations"
+    gen:
+      go:
+        emit_json_tags: true
+        package: "repository"
+        out: "db/repository"
+        sql_package: "pgx/v5"
+        overrides: 
+          - db_type: "pg_catalog.timestamp"
+            go_type:
+              import: "time"
+              type: "Time"
+          - db_type: "pg_catalog.timestamp"
+            nullable: true
+            go_type:
+              pointer: true
+              import: "time"
+              type: "Time"
+          - db_type: "pg_catalog.varchar"
+            nullable: true
+            go_type:
+              pointer: true
+              type: "string"
+          - db_type: "int4"
+            nullable: true
+            go_type:
+              pointer: true
+              type: "int32"
+          - db_type: "date"
+            nullable: false
+            go_type:
+              import: "time"
+              type: "Time"