smtp + email confirmation (#285)

* add smtp configuration

* add email confirm + reset templates

* add email sender to testrig

* flesh out the email sender interface

* go fmt

* golint

* update from field with more clarity

* tidy up the email formatting

* fix tests

* add email sender to processor

* tidy client api processing a bit

* further tidying in fromClientAPI

* pin new account to user

* send msg to processor on new account creation

* generate confirm email uri

* remove emailer from account processor again

* add processCreateAccountFromClientAPI

* move emailer accountprocessor => userprocessor

* add email sender to user processor

* SendConfirmEmail function

* add noop email sender

* use noop email sender in tests

* only assemble message if callback is not nil

* use noop email sender if no smtp host is defined

* minify email html before sending

* fix wrong email address

* email confirm test

* fmt

* serve web hndler

* add email confirm handler

* init test log properly on testrig

* log emails that *would* have been sent

* go fmt ./...

* unexport confirm email handler

* updatedAt

* test confirm email function

* don't allow tokens older than 7 days

* change error message a bit

* add basic smtp docs

* add a few more snippets

* typo

* add email sender to outbox tests

* don't use dutch wikipedia link

* don't minify email html

internal/email/util.go

@@ -0,0 +1,56 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 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 email
+
+import (
+	"fmt"
+	"html/template"
+	"os"
+	"path/filepath"
+)
+
+const (
+	mime = `MIME-version: 1.0;
+Content-Type: text/html;`
+)
+
+func loadTemplates(templateBaseDir string) (*template.Template, error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return nil, fmt.Errorf("error getting current working directory: %s", err)
+	}
+
+	// look for all templates that start with 'email_'
+	tmPath := filepath.Join(cwd, fmt.Sprintf("%semail_*", templateBaseDir))
+	return template.ParseGlob(tmPath)
+}
+
+func assembleMessage(mailSubject string, mailBody string, mailTo string, mailFrom string) []byte {
+	from := fmt.Sprintf("From: GoToSocial <%s>", mailFrom)
+	to := fmt.Sprintf("To: %s", mailTo)
+
+	msg := []byte(
+		mailSubject + "\r\n" +
+			from + "\r\n" +
+			to + "\r\n" +
+			mime + "\r\n" +
+			mailBody + "\r\n")
+
+	return msg
+}