MM-22405: Display the translated message instead of error id (#20462)

For a config failure, we now translate the message and show
a user friendly string rather than the error id.

This makes things easier to debug and read.

https://mattermost.atlassian.net/browse/MM-22405

```release-note
NONE
```

config/database_test.go

@@ -6,6 +6,7 @@ package config
 import (
 	"bytes"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -842,7 +843,9 @@ func TestDatabaseStoreLoad(t *testing.T) {
 
 		err = ds.Load()
 		if assert.Error(t, err) {
-			assert.EqualError(t, err, "invalid config: Config.IsValid: model.config.is_valid.site_url.app_error, parse \"invalid\": invalid URI for request")
+			var appErr *model.AppError
+			require.True(t, errors.As(err, &appErr))
+			assert.Equal(t, appErr.Id, "model.config.is_valid.site_url.app_error")
 		}
 	})
 

config/file_test.go

@@ -819,7 +819,9 @@ func TestFileStoreLoad(t *testing.T) {
 
 		err = fs.Load()
 		if assert.Error(t, err) {
-			assert.EqualError(t, err, "invalid config: Config.IsValid: model.config.is_valid.site_url.app_error, parse \"invalid\": invalid URI for request")
+			var appErr *model.AppError
+			require.True(t, errors.As(err, &appErr))
+			assert.Equal(t, appErr.Id, "model.config.is_valid.site_url.app_error")
 		}
 	})
 

config/store.go

@@ -12,6 +12,7 @@ import (
 	"github.com/pkg/errors"
 
 	"github.com/mattermost/mattermost-server/v6/model"
+	"github.com/mattermost/mattermost-server/v6/shared/i18n"
 	"github.com/mattermost/mattermost-server/v6/utils/jsonutils"
 )
 
@@ -293,8 +294,11 @@ func (s *Store) Load() error {
 
 	loadedCfg = applyEnvironmentMap(loadedCfg, GetEnvironment())
 	fixConfig(loadedCfg)
-	if err := loadedCfg.IsValid(); err != nil {
-		return errors.Wrap(err, "invalid config")
+	if appErr := loadedCfg.IsValid(); appErr != nil {
+		// Translating the error before displaying it in the console.
+		// Defaulting to english for server side language.
+		appErr.Translate(i18n.GetUserTranslations("en"))
+		return errors.Wrap(appErr, "invalid config")
 	}
 
 	// Backing up feature flags section in case we need to restore them later on.