feat: setup diesel & schema, course with metrics/audit tables

migrations/00000000000000_diesel_initial_setup/down.sql

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+-- This file was automatically created by Diesel to setup helper functions
+-- and other internal bookkeeping. This file is safe to edit, any future
+-- changes will be added to existing projects as new migrations.
+
+DROP FUNCTION IF EXISTS diesel_manage_updated_at(_tbl regclass);
+DROP FUNCTION IF EXISTS diesel_set_updated_at();

migrations/00000000000000_diesel_initial_setup/up.sql

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+-- This file was automatically created by Diesel to setup helper functions
+-- and other internal bookkeeping. This file is safe to edit, any future
+-- changes will be added to existing projects as new migrations.
+
+
+
+
+-- Sets up a trigger for the given table to automatically set a column called
+-- `updated_at` whenever the row is modified (unless `updated_at` was included
+-- in the modified columns)
+--
+-- # Example
+--
+-- ```sql
+-- CREATE TABLE users (id SERIAL PRIMARY KEY, updated_at TIMESTAMP NOT NULL DEFAULT NOW());
+--
+-- SELECT diesel_manage_updated_at('users');
+-- ```
+CREATE OR REPLACE FUNCTION diesel_manage_updated_at(_tbl regclass) RETURNS VOID AS $$
+BEGIN
+    EXECUTE format('CREATE TRIGGER set_updated_at BEFORE UPDATE ON %s
+                    FOR EACH ROW EXECUTE PROCEDURE diesel_set_updated_at()', _tbl);
+END;
+$$ LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION diesel_set_updated_at() RETURNS trigger AS $$
+BEGIN
+    IF (
+        NEW IS DISTINCT FROM OLD AND
+        NEW.updated_at IS NOT DISTINCT FROM OLD.updated_at
+    ) THEN
+        NEW.updated_at := current_timestamp;
+    END IF;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;

migrations/2025-08-27-231618_setup/down.sql

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+-- This file should undo anything in `up.sql`
+DROP TABLE IF EXISTS "courses";
+DROP TABLE IF EXISTS "course_metrics";
+DROP TABLE IF EXISTS "course_audits";

migrations/2025-08-27-231618_setup/up.sql

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+-- Your SQL goes here
+CREATE TABLE "courses"(
+	"id" INT4 NOT NULL PRIMARY KEY,
+	"crn" VARCHAR NOT NULL,
+	"subject" VARCHAR NOT NULL,
+	"course_number" VARCHAR NOT NULL,
+	"title" VARCHAR NOT NULL,
+	"term_code" VARCHAR NOT NULL,
+	"enrollment" INT4 NOT NULL,
+	"max_enrollment" INT4 NOT NULL,
+	"wait_count" INT4 NOT NULL,
+	"wait_capacity" INT4 NOT NULL,
+	"last_scraped_at" TIMESTAMPTZ NOT NULL
+);
+
+CREATE TABLE "course_metrics"(
+	"id" INT4 NOT NULL PRIMARY KEY,
+	"course_id" INT4 NOT NULL,
+	"timestamp" TIMESTAMPTZ NOT NULL,
+	"enrollment" INT4 NOT NULL,
+	"wait_count" INT4 NOT NULL,
+	"seats_available" INT4 NOT NULL,
+	FOREIGN KEY ("course_id") REFERENCES "courses"("id")
+);
+
+CREATE TABLE "course_audits"(
+	"id" INT4 NOT NULL PRIMARY KEY,
+	"course_id" INT4 NOT NULL,
+	"timestamp" TIMESTAMPTZ NOT NULL,
+	"field_changed" VARCHAR NOT NULL,
+	"old_value" TEXT NOT NULL,
+	"new_value" TEXT NOT NULL,
+	FOREIGN KEY ("course_id") REFERENCES "courses"("id")
+);
+