[chore] media and emoji refactoring (#3000)

* start updating media manager interface ready for storing attachments / emoji right away

* store emoji and media as uncached immediately, then (re-)cache on Processing{}.Load()

* remove now unused media workers

* fix tests and issues

* fix another test!

* fix emoji activitypub uri setting behaviour, fix remainder of test compilation issues

* fix more tests

* fix (most of) remaining tests, add debouncing to repeatedly failing media / emojis

* whoops, rebase issue

* remove kim's whacky experiments

* do some reshuffling, ensure emoji uri gets set

* ensure marked as not cached on cleanup

* tweaks to media / emoji processing to handle context canceled better

* ensure newly fetched emojis actually get set in returned slice

* use different varnames to be a bit more obvious

* move emoji refresh rate limiting to dereferencer

* add exported dereferencer functions for remote media, use these for recaching in processor

* add check for nil attachment in updateAttachment()

* remove unused emoji and media fields + columns

* see previous commit

* fix old migrations expecting image_updated_at to exists (from copies of old models)

* remove freshness checking code (seems to be broken...)

* fix error arg causing nil ptr exception

* finish documentating functions with comments, slight tweaks to media / emoji deref error logic

* remove some extra unneeded boolean checking

* finish writing documentation (code comments) for exported media manager methods

* undo changes to migration snapshot gtsmodels, updated failing migration to have its own snapshot

* move doesColumnExist() to util.go in migrations package

internal/api/fileserver/servefile_test.go

@@ -19,7 +19,7 @@ package fileserver_test
 
 import (
 	"context"
-	"io/ioutil"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -28,6 +28,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/api/fileserver"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/media"
+	"github.com/superseriousbusiness/gotosocial/internal/middleware"
 	"github.com/superseriousbusiness/gotosocial/testrig"
 )
 
@@ -54,12 +55,15 @@ func (suite *ServeFileTestSuite) GetFile(
 	ctx.AddParam(fileserver.MediaSizeKey, string(mediaSize))
 	ctx.AddParam(fileserver.FileNameKey, filename)
 
+	logger := middleware.Logger(false)
 	suite.fileServer.ServeFile(ctx)
+	logger(ctx)
+
 	code = recorder.Code
 	headers = recorder.Result().Header
 
 	var err error
-	body, err = ioutil.ReadAll(recorder.Body)
+	body, err = io.ReadAll(recorder.Body)
 	if err != nil {
 		suite.FailNow(err.Error())
 	}