Create user center slack and integrate with importer

[Anan1225]

OSPP project

1. Create user center Slack including login and authorization
2. Add notification slack type with upvoted, downvoted, etc.
3. Complete slash command function in Slack, /ask [Title][Context][Tag]

see issue151

[LinkinStars]

You need to update the README.

[LinkinStars]

remove the comment

[LinkinStars]

Here you can't write a fixed URL address, you can refer to the

incubator-answer-plugins/user-center-wecom/handler.go

Lines 55 to 64 in f10caf7

	func (uc *UserCenter) GetRedirectURL(ctx *gin.Context) {
	authorizeUrl := fmt.Sprintf("%s/answer/api/v1/user-center/login/callback", plugin.SiteURL())
	redirectURL := uc.Company.GetRedirectURL(authorizeUrl)
	state := genNonce()
	redirectURL = strings.ReplaceAll(redirectURL, "STATE", state)
	ctx.JSON(http.StatusOK, NewRespBodyData(http.StatusOK, "success", map[string]string{
	"redirect_url": redirectURL,
	"key": state,
	}))
	}

[LinkinStars]

Remove it.

[LinkinStars]

The comment maybe out of date.

[LinkinStars]

The way it is currently handled here results in a new ticker being started to synchronise the data every time the configuration is updated as long as AutoSync is true. On the one hand, we need to deal with the case where AutoSync is false, and on the other hand, we need to deal with the case where we can't turn on more than one at the same time. I hope this is understandable.

[LinkinStars]

Maybe some translations is out of date.

[LinkinStars]

Of course in most cases there is no problem with taking [1] directly. But it's safer to judge the internal length.