PLT-3077 Add group messaging (#5489)

* Implement server changes for group messaging

* Majority of client-side implementation

* Some server updates

* Added new React multiselect component

* Fix style issues

* Add custom renderer for options

* Fix model test

* Update ENTER functionality for multiselect control

* Remove buttons from multiselect UI control

* Updating group messaging UI (#5524)

* Move filter controls up a component level

* Scroll with arrow keys

* Updating mobile layout for multiselect (#5534)

* Fix race condition when backspacing quickly

* Hidden or new GMs show up for regular messages

* Add overriding of number remaining text

* Add UI filtering for team if config setting set

* Add icon to channel switcher and class prop to status icon

* Minor updates per feedback

* Improving group messaging UI (#5563)

* UX changes per feedback

* Update email for group messages

* UI fixes for group messaging (#5587)

* Fix missing localization string

* Add maximum users message when adding members to GM

* Fix input clearing on Android

* Updating group messaging UI (#5603)

* Updating UI for group messaging (#5604)

model/channel.go

@@ -4,8 +4,12 @@
 package model
 
 import (
+	"crypto/sha1"
+	"encoding/hex"
 	"encoding/json"
 	"io"
+	"sort"
+	"strings"
 	"unicode/utf8"
 )
 
@@ -13,6 +17,9 @@ const (
 	CHANNEL_OPEN                   = "O"
 	CHANNEL_PRIVATE                = "P"
 	CHANNEL_DIRECT                 = "D"
+	CHANNEL_GROUP                  = "G"
+	CHANNEL_GROUP_MAX_USERS        = 8
+	CHANNEL_GROUP_MIN_USERS        = 3
 	DEFAULT_CHANNEL                = "town-square"
 	CHANNEL_DISPLAY_NAME_MAX_RUNES = 64
 	CHANNEL_NAME_MIN_LENGTH        = 2
@@ -89,7 +96,7 @@ func (o *Channel) IsValid() *AppError {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+o.Id)
 	}
 
-	if !(o.Type == CHANNEL_OPEN || o.Type == CHANNEL_PRIVATE || o.Type == CHANNEL_DIRECT) {
+	if !(o.Type == CHANNEL_OPEN || o.Type == CHANNEL_PRIVATE || o.Type == CHANNEL_DIRECT || o.Type == CHANNEL_GROUP) {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.type.app_error", nil, "id="+o.Id)
 	}
 
@@ -126,6 +133,10 @@ func (o *Channel) ExtraUpdated() {
 	o.ExtraUpdateAt = GetMillis()
 }
 
+func (o *Channel) IsGroupOrDirect() bool {
+	return o.Type == CHANNEL_DIRECT || o.Type == CHANNEL_GROUP
+}
+
 func GetDMNameFromIds(userId1, userId2 string) string {
 	if userId1 > userId2 {
 		return userId2 + "__" + userId1
@@ -133,3 +144,31 @@ func GetDMNameFromIds(userId1, userId2 string) string {
 		return userId1 + "__" + userId2
 	}
 }
+
+func GetGroupDisplayNameFromUsers(users []*User, truncate bool) string {
+	usernames := make([]string, len(users))
+	for index, user := range users {
+		usernames[index] = user.Username
+	}
+
+	sort.Strings(usernames)
+
+	name := strings.Join(usernames, ", ")
+
+	if truncate && len(name) > CHANNEL_NAME_MAX_LENGTH {
+		name = name[:CHANNEL_NAME_MAX_LENGTH]
+	}
+
+	return name
+}
+
+func GetGroupNameFromUserIds(userIds []string) string {
+	sort.Strings(userIds)
+
+	h := sha1.New()
+	for _, id := range userIds {
+		io.WriteString(h, id)
+	}
+
+	return hex.EncodeToString(h.Sum(nil))
+}