Remove links check_duration column

We will have enough realtime statistics from the new link checker,
so we don't need to store this in the database

Author: AMDmi3

migrate.sql

@@ -0,0 +1,14 @@
+alter table packages add column pkgconfig_names text[] NULL;
+
+CREATE TYPE project_identifier_type AS enum(
+	'pkgconfig'
+);
+
+CREATE TABLE project_identifiers (
+	project_id integer NOT NULL,
+	"type" project_identifier_type NOT NULL,
+	identifier text NOT NULL
+);
+
+CREATE INDEX ON project_identifiers(project_id);
+CREATE INDEX ON project_identifiers(identifier);

sql.d/schema/create_schema_tables.sql

@@ -506,9 +506,7 @@ CREATE TABLE links (
 	ipv6_last_failure timestamp with time zone,
 	ipv6_success boolean,
 	ipv6_status_code smallint,
-	ipv6_permanent_redirect_target text,
-
-	check_duration real
+	ipv6_permanent_redirect_target text
 );
 
 CREATE UNIQUE INDEX ON links(url);