[security] transport.Controller{} and transport.Transport{} security and performance improvements (#564)

* cache transports in controller by privkey-generated pubkey, add retry logic to transport requests

Signed-off-by: kim <grufwub@gmail.com>

* update code comments, defer mutex unlocks

Signed-off-by: kim <grufwub@gmail.com>

* add count to 'performing request' log message

Signed-off-by: kim <grufwub@gmail.com>

* reduce repeated conversions of same url.URL object

Signed-off-by: kim <grufwub@gmail.com>

* move worker.Worker to concurrency subpackage, add WorkQueue type, limit transport http client use by WorkQueue

Signed-off-by: kim <grufwub@gmail.com>

* fix security advisories regarding max outgoing conns, max rsp body size

- implemented by a new httpclient.Client{} that wraps an underlying
  client with a queue to limit connections, and limit reader wrapping
  a response body with a configured maximum size
- update pub.HttpClient args passed around to be this new httpclient.Client{}

Signed-off-by: kim <grufwub@gmail.com>

* add httpclient tests, move ip validation to separate package + change mechanism

Signed-off-by: kim <grufwub@gmail.com>

* fix merge conflicts

Signed-off-by: kim <grufwub@gmail.com>

* use singular mutex in transport rather than separate signer mus

Signed-off-by: kim <grufwub@gmail.com>

* improved useragent string

Signed-off-by: kim <grufwub@gmail.com>

* add note regarding missing test

Signed-off-by: kim <grufwub@gmail.com>

* remove useragent field from transport (instead store in controller)

Signed-off-by: kim <grufwub@gmail.com>

* shutup linter

Signed-off-by: kim <grufwub@gmail.com>

* reset other signing headers on each loop iteration

Signed-off-by: kim <grufwub@gmail.com>

* respect request ctx during retry-backoff sleep period

Signed-off-by: kim <grufwub@gmail.com>

* use external pkg with docs explaining performance "hack"

Signed-off-by: kim <grufwub@gmail.com>

* use http package constants instead of string method literals

Signed-off-by: kim <grufwub@gmail.com>

* add license file headers

Signed-off-by: kim <grufwub@gmail.com>

* update code comment to match new func names

Signed-off-by: kim <grufwub@gmail.com>

* updates to user-agent string

Signed-off-by: kim <grufwub@gmail.com>

* update signed testrig models to fit with new transport logic (instead uses separate signer now)

Signed-off-by: kim <grufwub@gmail.com>

* fuck you linter

Signed-off-by: kim <grufwub@gmail.com>

internal/api/s2s/webfinger/webfingerget_test.go

@@ -31,10 +31,10 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/suite"
 	"github.com/superseriousbusiness/gotosocial/internal/api/s2s/webfinger"
+	"github.com/superseriousbusiness/gotosocial/internal/concurrency"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/messages"
 	"github.com/superseriousbusiness/gotosocial/internal/processing"
-	"github.com/superseriousbusiness/gotosocial/internal/worker"
 	"github.com/superseriousbusiness/gotosocial/testrig"
 )
 
@@ -71,8 +71,8 @@ func (suite *WebfingerGetTestSuite) TestFingerUser() {
 func (suite *WebfingerGetTestSuite) TestFingerUserWithDifferentAccountDomainByHost() {
 	viper.Set(config.Keys.Host, "gts.example.org")
 	viper.Set(config.Keys.AccountDomain, "example.org")
-	clientWorker := worker.New[messages.FromClientAPI](-1, -1)
-	fedWorker := worker.New[messages.FromFederator](-1, -1)
+	clientWorker := concurrency.NewWorkerPool[messages.FromClientAPI](-1, -1)
+	fedWorker := concurrency.NewWorkerPool[messages.FromFederator](-1, -1)
 	suite.processor = processing.NewProcessor(suite.tc, suite.federator, testrig.NewTestOauthServer(suite.db), testrig.NewTestMediaManager(suite.db, suite.storage), suite.storage, suite.db, suite.emailSender, clientWorker, fedWorker)
 	suite.webfingerModule = webfinger.New(suite.processor).(*webfinger.Module)
 
@@ -107,8 +107,8 @@ func (suite *WebfingerGetTestSuite) TestFingerUserWithDifferentAccountDomainByHo
 func (suite *WebfingerGetTestSuite) TestFingerUserWithDifferentAccountDomainByAccountDomain() {
 	viper.Set(config.Keys.Host, "gts.example.org")
 	viper.Set(config.Keys.AccountDomain, "example.org")
-	clientWorker := worker.New[messages.FromClientAPI](-1, -1)
-	fedWorker := worker.New[messages.FromFederator](-1, -1)
+	clientWorker := concurrency.NewWorkerPool[messages.FromClientAPI](-1, -1)
+	fedWorker := concurrency.NewWorkerPool[messages.FromFederator](-1, -1)
 	suite.processor = processing.NewProcessor(suite.tc, suite.federator, testrig.NewTestOauthServer(suite.db), testrig.NewTestMediaManager(suite.db, suite.storage), suite.storage, suite.db, suite.emailSender, clientWorker, fedWorker)
 	suite.webfingerModule = webfinger.New(suite.processor).(*webfinger.Module)