[chore] Global server configuration overhaul (#575)

* move config flag names and usage to config package, rewrite config package to use global Configuration{} struct

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

* improved code comment

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

* linter

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

* fix unmarshaling

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

* remove kim's custom go compiler changes

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

* generate setter and flag-name functions, implement these in codebase

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

* update deps

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

* small change

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

* appease the linter...

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

* move configuration into ConfigState structure, ensure reloading to/from viper settings to keep in sync

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

* lint

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

* update code comments

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

* fix merge issue

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

* fix merge issue

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

* improved version string (removes time + go version)

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

* fix version string build to pass test script + consolidate logic in func

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

* add license text, update config.Defaults comment

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

* add license text to generated config helpers file

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

* defer unlock on config.Set___(), to ensure unlocked on panic

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

* make it more obvious which cmd flags are being attached

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

testrig/email.go

@@ -19,7 +19,6 @@
 package testrig
 
 import (
-	"github.com/spf13/viper"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/email"
 )
@@ -30,7 +29,9 @@ import (
 // the map, with email address of the recipient as the key, and the value as the
 // parsed email message as it would have been sent.
 func NewEmailSender(templateBaseDir string, sentEmails map[string]string) email.Sender {
-	viper.Set(config.Keys.WebTemplateBaseDir, templateBaseDir)
+	config.Config(func(cfg *config.Configuration) {
+		cfg.WebTemplateBaseDir = templateBaseDir
+	})
 
 	var sendCallback func(toAddress string, message string)