Add migration notes for later

redxen/postgresql/TODO.md

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+# Migration TODO's / Instructions for 13->17
+
+- Stop all services except DB
+- pg_dumpall from live DB
+- Init DB + Load dump manually
+- Correct permission set to be matching expectations:
+
+```
+CREATE ROLE "mail" LOGIN;
+ALTER DATABASE "mail" OWNER TO "mail";
+
+REASSIGN OWNED BY "postfix" TO "mail";
+DROP OWNED BY "postfix";
+DROP ROLE "postfix";
+
+REASSIGN OWNED BY "dovecot" TO "mail";
+DROP OWNED BY "dovecot";
+DROP ROLE "dovecot";
+
+CREATE ROLE "postfix" LOGIN;
+GRANT "mail" TO "postfix";
+CREATE ROLE "dovecot" LOGIN;
+GRANT "mail" TO "dovecot";
+
+ALTER DATABASE "gitea" OWNER TO "gitea";
+
+CREATE ROLE "keycloak" LOGIN;
+CREATE DATABASE "keycloak" OWNER "keycloak";
+
+CREATE ROLE "exporter" LOGIN;
+GRANT "postgres" TO "exporter";
+```
+
+## Quicker alternative - Modify the dump as follows
+- Delete any role creations, those are handled by the initdb
+- Revert any database creations, those are handled by the dump
+- Modify OWNER TO's to be correct
+
+```
+DROP DATABASE gitea;
+DROP DATABASE grafana;
+DROP DATABASE mail;
+DROP DATABASE murmur;
+```
+
+```
+< dump.sql sed \
+    -e 's/OWNER TO postfix;/OWNER TO mail;/g' \
+    -e 's/OWNER TO dovecot;/OWNER TO mail;/g' \
+    -e 's/ALTER DATABASE gitea OWNER TO postgres;/ALTER DATABASE gitea OWNER TO gitea;/' \
+    -e 's/ALTER DATABASE mail OWNER TO postgres;/ALTER DATABASE mail OWNER TO mail;/' \
+| grep -v '^CREATE ROLE .*;$' | grep -v '^ALTER ROLE .*;$'
+```