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

src/PostgREST/App.hs

@@ -220,7 +220,7 @@ handleRequest AuthResult{..} conf appState authenticated prepared pgVer apiReq@A
       return $ pgrstResponse metrics  pgrst
 
     (ActionInspect headersOnly, TargetDefaultSpec tSchema) -> do
-      (planTime', iPlan) <- withTiming $ liftEither $ Plan.inspectPlan conf apiReq
+      (planTime', iPlan) <- withTiming $ liftEither $ Plan.inspectPlan apiReq
       (rsTime', oaiResult) <- withTiming $ runQuery roleIsoLvl (Plan.ipTxmode iPlan) $ Query.openApiQuery sCache pgVer conf tSchema
       (renderTime', pgrst) <- withTiming $ liftEither $ Response.openApiResponse (T.decodeUtf8 prettyVersion, docsVersion) headersOnly oaiResult conf sCache iSchema iNegotiatedByProfile
       let metrics = Map.fromList [(SMPlan, planTime'), (SMQuery, rsTime'), (SMRender, renderTime'), jwtTime]