add history to edit_host

Hosts now have history.

host table was split to host (containing ephemereal and non-editable
data (load, activity, name, user_id)) and host_config containing
data changeable by admins (archs, capacity, ...). This table is
versioned and searchable via queryHistory.

Fixes: https://pagure.io/koji/issue/638

docs/schema-upgrade-1.15-1.16.sql

@@ -0,0 +1,47 @@
+-- upgrade script to migrate the Koji database schema
+-- from version 1.13 to 1.14
+
+
+BEGIN;
+
+-- create host_config table
+SELECT 'Creating table host_config';
+CREATE TABLE host_config (
+        host_id INTEGER NOT NULL REFERENCES host(id),
+	arches TEXT,
+	capacity FLOAT CHECK (capacity > 1) NOT NULL DEFAULT 2.0,
+	description TEXT,
+	comment TEXT,
+	enabled BOOLEAN NOT NULL DEFAULT 'true',
+-- versioned - see desc above
+	create_event INTEGER NOT NULL REFERENCES events(id) DEFAULT get_event(),
+	revoke_event INTEGER REFERENCES events(id),
+	creator_id INTEGER NOT NULL REFERENCES users(id),
+	revoker_id INTEGER REFERENCES users(id),
+	active BOOLEAN DEFAULT 'true' CHECK (active),
+	CONSTRAINT active_revoke_sane CHECK (
+		(active IS NULL AND revoke_event IS NOT NULL AND revoker_id IS NOT NULL)
+		OR (active IS NOT NULL AND revoke_event IS NULL AND revoker_id IS NULL)),
+	PRIMARY KEY (create_event, host_id),
+	UNIQUE (host_id,active)
+) WITHOUT OIDS;
+
+-- copy starting data
+-- CREATE FUNCTION pg_temp.user() returns INTEGER as $$ select id from users where name='nobody' $$ language SQL;
+CREATE FUNCTION pg_temp.user() returns INTEGER as $$ select 1 $$ language SQL;
+-- If you would like to use an existing user instead, then:
+--   1. edit the temporary function to look for the alternate user name
+
+SELECT 'Copying data from host to host_config';
+INSERT INTO host_config (host_id, arches, capacity, description, comment, enabled, creator_id)
+        SELECT id, arches, capacity, description, comment, enabled, pg_temp.user() FROM host;
+
+-- alter original table
+SELECT 'Dropping moved columns';
+ALTER TABLE host DROP COLUMN arches;
+ALTER TABLE host DROP COLUMN capacity;
+ALTER TABLE host DROP COLUMN description;
+ALTER TABLE host DROP COLUMN comment;
+ALTER TABLE host DROP COLUMN enabled;
+
+COMMIT;