feat: sql handlers for custom media types

* test text/html and drop HtmlRawOutputSpec.hs
* all tests passing, removed all pendingWith
* make functions compatible with pg <= 12
* move custom media types tests to own spec
* anyelement aggregate
* apply aggregates without a final function
* overriding works
* overriding anyelement with particular agg
* cannot override vendored media types
* plan spec works with custom aggregate
* renamed media types to make clear which ones are overridable
* correct content negotiation with same weight
* text/tab-separated-values media type
* text/csv with BOM plus content-disposition header

test/spec/fixtures/data.sql

@@ -858,3 +858,6 @@ TRUNCATE TABLE table_a CASCADE;
 INSERT INTO table_a(id, name) VALUES (1, 'Not null 1'), (2, null), (3, 'Not null 2');
 TRUNCATE TABLE table_b CASCADE;
 INSERT INTO table_b(table_a_id, name) VALUES (1, 'Test 1'), (2, 'Test 2'), (null, 'Test 3');
+
+TRUNCATE TABLE lines CASCADE;
+insert into lines values (1, 'line-1', 'LINESTRING(1 1,5 5)'::extensions.geometry), (2, 'line-2', 'LINESTRING(2 2,6 6)'::extensions.geometry);