Add scripts for database migration

db/migrations/0002-optimise-profile-content.sql

@@ -0,0 +1,16 @@
+-- Change hashed_profile_content column affinity to INTEGER
+
+CREATE TABLE "new_sim_member" (
+	"mxid"	TEXT NOT NULL,
+	"room_id"	TEXT NOT NULL,
+	"hashed_profile_content"	INTEGER,
+	PRIMARY KEY("room_id","mxid")
+) WITHOUT ROWID;
+
+INSERT INTO new_sim_member SELECT * FROM sim_member;
+
+DROP TABLE sim_member;
+
+ALTER TABLE new_sim_member RENAME TO sim_member;
+
+VACUUM;