[feature] Set/show instance language(s); show post language on frontend (#2362)

* update go text, include text/display

* [feature] Set instance langs, show post lang on frontend

* go fmt

* WebGet

* set language for whole article, don't use FA icon

* mention instance languages + other optional config vars

* little tweak

* put languages in config properly

* warn log language parse

* change some naming around

* tidy up validate a bit

* lint

* rename LanguageTmpl in template

3 files changed, 34 insertions, 6 deletions

diff --git a/internal/typeutils/converter_test.go b/internal/typeutils/converter_test.go
index 122b98d4c..0195a6889 100644
--- a/internal/typeutils/converter_test.go
+++ b/internal/typeutils/converter_test.go
@@ -526,7 +526,7 @@ func (suite *TypeUtilsTestSuite) GetProcessor() *processing.Processor {
 	mediaManager := testrig.NewTestMediaManager(&suite.state)
 	federator := testrig.NewTestFederator(&suite.state, transportController, mediaManager)
 	emailSender := testrig.NewEmailSender("../../web/template/", nil)
-	
+
 	processor := testrig.NewTestProcessor(&suite.state, federator, emailSender, mediaManager)
 	testrig.StartWorkers(&suite.state, processor.Workers())
 
diff --git a/internal/typeutils/internaltofrontend.go b/internal/typeutils/internaltofrontend.go
index 1a2c321f5..8138ee7b4 100644
--- a/internal/typeutils/internaltofrontend.go
+++ b/internal/typeutils/internaltofrontend.go
@@ -30,6 +30,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/language"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
 	"github.com/superseriousbusiness/gotosocial/internal/media"
 	"github.com/superseriousbusiness/gotosocial/internal/uris"
@@ -656,7 +657,28 @@ func (c *Converter) StatusToWebStatus(
 	s *gtsmodel.Status,
 	requestingAccount *gtsmodel.Account,
 ) (*apimodel.Status, error) {
-	return c.statusToFrontend(ctx, s, requestingAccount)
+	webStatus, err := c.statusToFrontend(ctx, s, requestingAccount)
+	if err != nil {
+		return nil, err
+	}
+
+	// Add additional information for template.
+	// Assume empty langs, hope for not empty language.
+	webStatus.LanguageTag = new(language.Language)
+	if lang := webStatus.Language; lang != nil {
+		langTag, err := language.Parse(*lang)
+		if err != nil {
+			log.Warnf(
+				ctx,
+				"error parsing %s as language tag: %v",
+				*lang, err,
+			)
+		} else {
+			webStatus.LanguageTag = langTag
+		}
+	}
+
+	return webStatus, nil
 }
 
 // statusToFrontend is a package internal function for
@@ -873,7 +895,7 @@ func (c *Converter) InstanceToAPIV1Instance(ctx context.Context, i *gtsmodel.Ins
 		ShortDescription: i.ShortDescription,
 		Email:            i.ContactEmail,
 		Version:          config.GetSoftwareVersion(),
-		Languages:        []string{}, // todo: not supported yet
+		Languages:        config.GetInstanceLanguages().TagStrs(),
 		Registrations:    config.GetAccountsRegistrationOpen(),
 		ApprovalRequired: config.GetAccountsApprovalRequired(),
 		InvitesEnabled:   false, // todo: not supported yet
@@ -982,7 +1004,7 @@ func (c *Converter) InstanceToAPIV2Instance(ctx context.Context, i *gtsmodel.Ins
 		SourceURL:     instanceSourceURL,
 		Description:   i.Description,
 		Usage:         apimodel.InstanceV2Usage{}, // todo: not implemented
-		Languages:     []string{},                 // todo: not implemented
+		Languages:     config.GetInstanceLanguages().TagStrs(),
 		Rules:         c.InstanceRulesToAPIRules(i.Rules),
 		Terms:         i.Terms,
 	}
diff --git a/internal/typeutils/internaltofrontend_test.go b/internal/typeutils/internaltofrontend_test.go
index d386c180e..ee8216e8f 100644
--- a/internal/typeutils/internaltofrontend_test.go
+++ b/internal/typeutils/internaltofrontend_test.go
@@ -712,7 +712,10 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV1ToFrontend() {
   "short_description": "\u003cp\u003eThis is the GoToSocial testrig. It doesn't federate or anything.\u003c/p\u003e\u003cp\u003eWhen the testrig is shut down, all data on it will be deleted.\u003c/p\u003e\u003cp\u003eDon't use this in production!\u003c/p\u003e",
   "email": "admin@example.org",
   "version": "0.0.0-testrig",
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "registrations": true,
   "approval_required": true,
   "invites_enabled": false,
@@ -826,7 +829,10 @@ func (suite *InternalToFrontendTestSuite) TestInstanceV2ToFrontend() {
   "thumbnail": {
     "url": "http://localhost:8080/assets/logo.png"
   },
-  "languages": [],
+  "languages": [
+    "nl",
+    "en-gb"
+  ],
   "configuration": {
     "urls": {
       "streaming": "wss://localhost:8080"