[bugfix] Fix HTML escaping in instance title (#607)

* move caption sanitization -> sanitize.go

* use sanitizeplaintext rather than removehtml

* rename sanitizecaption to sanitizeplaintext

* avoid removing html twice from statuses

* unexport remoteHTML
it's no longer used outside the text package so this
makes it less confusing

* test instance PATCH

internal/text/removehtml_test.go

@@ -0,0 +1,57 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package text
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+)
+
+const (
+	test_removeHTML                 = `<p>Another test <span class="h-card"><a href="http://fossbros-anonymous.io/@foss_satan" class="u-url mention" rel="nofollow noreferrer noopener" target="_blank">@<span>foss_satan</span></a></span><br/><br/><a href="http://localhost:8080/tags/Hashtag" class="mention hashtag" rel="tag nofollow noreferrer noopener" target="_blank">#<span>Hashtag</span></a><br/><br/>Text</p>`
+	test_removedHTML                = `Another test @foss_satan#HashtagText`
+	test_withEscapedLiteral         = `it\u0026amp;#39;s its it is`
+	test_withEscapedLiteralExpected = `it\u0026amp;#39;s its it is`
+	test_withEscaped                = "it\u0026amp;#39;s its it is"
+	test_withEscapedExpected        = "it&amp;#39;s its it is"
+)
+
+type RemoveHTMLTestSuite struct {
+	suite.Suite
+}
+
+func (suite *RemoveHTMLTestSuite) TestSanitizeWithEscapedLiteral() {
+	s := removeHTML(test_withEscapedLiteral)
+	suite.Equal(test_withEscapedLiteralExpected, s)
+}
+
+func (suite *RemoveHTMLTestSuite) TestSanitizeWithEscaped() {
+	s := removeHTML(test_withEscaped)
+	suite.Equal(test_withEscapedExpected, s)
+}
+
+func (suite *RemoveHTMLTestSuite) TestRemoveHTML() {
+	s := removeHTML(test_removeHTML)
+	suite.Equal(test_removedHTML, s)
+}
+
+func TestRemoveHTMLTestSuite(t *testing.T) {
+	suite.Run(t, &RemoveHTMLTestSuite{})
+}