feat: add kit_last_seen table migrations

migrations/2024-03-15-155708_create_kit_last_seen/down.sql

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+DROP TABLE kit_last_seen;

migrations/2024-03-15-155708_create_kit_last_seen/up.sql

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+CREATE TABLE kit_last_seen (
+    kit_id int4 NOT NULL,
+    datetime_last_seen timestamptz NOT NULL,
+    CONSTRAINT kit_last_seen_pkey PRIMARY KEY (kit_id)
+);
+
+CREATE INDEX ix_kit_last_seen_datetime_last_seen ON public.kit_last_seen USING btree (datetime_last_seen);
+
+-- foreign keys
+ALTER TABLE public.kit_last_seen
+    ADD CONSTRAINT kit_last_seen_kit_id_fkey FOREIGN KEY (kit_id) REFERENCES kits (id) ON DELETE CASCADE ON UPDATE CASCADE;

migrations/2024-03-15-161913_populate_kit_last_seen/down.sql

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+-- no-op
+SELECT 1;

migrations/2024-03-15-161913_populate_kit_last_seen/up.sql

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+INSERT INTO kit_last_seen
+SELECT
+    kit_id,
+    MAX(datetime_start) AS datetime_last_seen
+FROM
+    aggregate_measurements
+GROUP BY
+    kit_id
+ON CONFLICT
+    DO NOTHING;