Make log mailer for testing

[zeripath]

Multiple users have noticed in problems in 1.7.0 with issues to do with sending email. This is because there are code paths to do with emailing that are not tested in the integrations test due to gitea requiring a valid email configuration.

This PR creates a simple log mailer that can be used to test what kind of emails gitea would send.

Of note cherry-picking this and placing it on the v1.7 release master reveals the underlying bug in #5891.

[zeripath]

Shortened log after cherry-picking this and placing it on releases/v1.7:

[Macaron] 2019-01-29 20:58:44: Started POST /api/v1/repos/user2/repo1/issues/1/comments?token=8a500d363a99c101fe1be475886b62fc0712947c for 
[Macaron] PANIC: runtime error: invalid memory address or nil pointer dereference
/usr/lib/go-1.10/src/runtime/panic.go:502 (0x438968)
	gopanic: reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
/usr/lib/go-1.10/src/runtime/panic.go:63 (0x4377fd)
	panicmem: panic(memoryError)
/usr/lib/go-1.10/src/runtime/signal_unix.go:388 (0x44e519)
	sigpanic: panicmem()
/home/andrew/go/src/code.gitea.io/gitea/models/issue_mail.go:81 (0xe55e31)
	mailIssueCommentToParticipants: if participants[i].ID == doer.ID {
/home/andrew/go/src/code.gitea.io/gitea/models/issue_comment.go:378 (0xe45d3c)
	(*Comment).MailParticipants: if err = mailIssueCommentToParticipants(e, issue, c.Poster, content, c, mentions); err != nil {
/home/andrew/go/src/code.gitea.io/gitea/models/issue_comment.go:635 (0xe4788f)
	sendCreateCommentAction: if err = comment.MailParticipants(e, act.OpType, opts.Issue); err != nil {
/home/andrew/go/src/code.gitea.io/gitea/models/issue_comment.go:533 (0xe46e2a)
	createComment: if err = sendCreateCommentAction(e, opts, comment); err != nil {
/home/andrew/go/src/code.gitea.io/gitea/models/issue_comment.go:814 (0xe48ac3)
	CreateComment: comment, err = createComment(sess, opts)
/home/andrew/go/src/code.gitea.io/gitea/models/issue_comment.go:831 (0xe48ca0)
	CreateIssueComment: comment, err := CreateComment(&CreateCommentOptions{
/home/andrew/go/src/code.gitea.io/gitea/routers/api/v1/repo/issue_comment.go:172 (0x1074fb0)

Revealing immediately the bug described in #5891

[codecov-io]

Codecov Report

Merging #5893 into master will increase coverage by 0.24%.
The diff coverage is 34.78%.

@@            Coverage Diff             @@
##           master    #5893      +/-   ##
==========================================
+ Coverage   37.98%   38.22%   +0.24%     
==========================================
  Files         329      329              
  Lines       48406    48423      +17     
==========================================
+ Hits        18385    18508     +123     
+ Misses      27379    27249     -130     
- Partials     2642     2666      +24

Impacted Files	Coverage Δ
modules/setting/setting.go	51.71% <10%> (+2.34%)	⬆️
modules/mailer/mailer.go	22.04% <53.84%> (+18.08%)	⬆️
models/repo_list.go	63.29% <0%> (-1.27%)	⬇️
routers/user/auth.go	13.28% <0%> (ø)	⬆️
models/issue.go	47.59% <0%> (+0.25%)	⬆️
modules/markup/markup.go	79.03% <0%> (+9.67%)	⬆️
models/mail.go	24.13% <0%> (+22.41%)	⬆️
models/issue_mail.go	53.84% <0%> (+42.3%)	⬆️

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[lafriks]

I would prefer that inbucket service would be added to drone builds and that be used as SMTP server. Than no new fake tyoe would not be needed and later we could use it's api to check if message is actually sent

[zeripath]

Ok, I can understand that. I did wonder if we should make an internal channeled debug mailer myself - one that would just create a list of mail objects sent so you could query it in integration tests.

There may still be a point to having this sort of log mailer though. You can have it set on your development machine and test what is going to come out of Gitea without having to set up other servers. (Although you can kind of do this with the sendmail interface this would be built in unless we wanted to provide an appropriate sendmail proxy script.)

In any case, the point was to spur us to sort this out. We went live with a fairly major version and server 500s happened as soon as people turned on email notifications.

[lunny]

Maybe we should name it dummy or testing but not a log because it only is used for testing. And that could be saved on a memory map or channel to confirm the testing but not on a log file.

[techknowlogick]

This PR looks great! I'm happy to give my 👍, but I like @lunny's idea of changing the name to testing, dummy, or something like that.

[zeripath]

Hi @techknowlogick Have changed it to dummy which I think is a good representation of what it is. We can make a testing one at some point which could be channel based. But at least with this we can test the emailing pathways.