PLT-6965 jira integration (plus plugin scaffolding) (#6918)

* plugin scaffolding / jira integration

* add vendored testify packages

* webhook fix

* don't change i18n ids

* support configuration watching

* add basic jira plugin configuration to admin console

* fix eslint errors

* fix another eslint warning

* polish

* undo unintentional config.json commit >:(

* test fix

* add jira plugin diagnostics, remove dm support, add bot tag, generate web-safe secrets

* rebase, implement requested changes

* requested changes

* remove tests and minimize makefile change

* add missing license headers

* add missing comma

* remove bad line from Makefile

app/plugins.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package app
+
+import (
+	"encoding/json"
+	"net/http"
+
+	l4g "github.com/alecthomas/log4go"
+
+	"github.com/gorilla/mux"
+	"github.com/mattermost/platform/model"
+	"github.com/mattermost/platform/utils"
+
+	"github.com/mattermost/platform/app/plugin"
+	"github.com/mattermost/platform/app/plugin/jira"
+)
+
+type PluginAPI struct {
+	id     string
+	router *mux.Router
+}
+
+func (api *PluginAPI) LoadPluginConfiguration(dest interface{}) error {
+	if b, err := json.Marshal(utils.Cfg.PluginSettings.Plugins[api.id]); err != nil {
+		return err
+	} else {
+		return json.Unmarshal(b, dest)
+	}
+}
+
+func (api *PluginAPI) PluginRouter() *mux.Router {
+	return api.router
+}
+
+func (api *PluginAPI) GetTeamByName(name string) (*model.Team, *model.AppError) {
+	return GetTeamByName(name)
+}
+
+func (api *PluginAPI) GetUserByName(name string) (*model.User, *model.AppError) {
+	return GetUserByUsername(name)
+}
+
+func (api *PluginAPI) GetChannelByName(teamId, name string) (*model.Channel, *model.AppError) {
+	return GetChannelByName(name, teamId)
+}
+
+func (api *PluginAPI) GetDirectChannel(userId1, userId2 string) (*model.Channel, *model.AppError) {
+	return GetDirectChannel(userId1, userId2)
+}
+
+func (api *PluginAPI) CreatePost(post *model.Post, teamId string) (*model.Post, *model.AppError) {
+	return CreatePost(post, teamId, true)
+}
+
+func (api *PluginAPI) I18n(id string, r *http.Request) string {
+	if r != nil {
+		f, _ := utils.GetTranslationsAndLocale(nil, r)
+		return f(id)
+	}
+	f, _ := utils.GetTranslationsBySystemLocale()
+	return f(id)
+}
+
+func InitPlugins() {
+	plugins := map[string]plugin.Plugin{
+		"jira": &jira.Plugin{},
+	}
+	for id, p := range plugins {
+		l4g.Info("Initializing plugin: " + id)
+		api := &PluginAPI{
+			id:     id,
+			router: Srv.Router.PathPrefix("/plugins/" + id).Subrouter(),
+		}
+		p.Initialize(api)
+	}
+	utils.AddConfigListener(func(before, after *model.Config) {
+		for _, p := range plugins {
+			p.OnConfigurationChange()
+		}
+	})
+	for _, p := range plugins {
+		p.OnConfigurationChange()
+	}
+}