v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/model/thread.go

@@ -0,0 +1,128 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+// Thread tracks the metadata associated with a root post and its reply posts.
+//
+// Note that Thread metadata does not exist until the first reply to a root post.
+type Thread struct {
+	// PostId is the root post of the thread.
+	PostId string `json:"id"`
+
+	// ChannelId is the channel in which the thread was posted.
+	ChannelId string `json:"channel_id"`
+
+	// ReplyCount is the number of replies to the thread (excluding deleted posts).
+	ReplyCount int64 `json:"reply_count"`
+
+	// LastReplyAt is the timestamp of the most recent post to the thread.
+	LastReplyAt int64 `json:"last_reply_at"`
+
+	// Participants is a list of user ids that have replied to the thread, sorted by the oldest
+	// to newest. Note that the root post author is not included in this list until they reply.
+	Participants StringArray `json:"participants"`
+
+	// DeleteAt is a denormalized copy of the root posts's DeleteAt. In the database, it's
+	// named ThreadDeleteAt to avoid introducing a query conflict with older server versions.
+	DeleteAt int64 `json:"delete_at"`
+
+	// TeamId is a denormalized copy of the Channel's teamId. In the database, it's
+	// named ThreadTeamId to avoid introducing a query conflict with older server versions.
+	TeamId string `json:"team_id"`
+}
+
+type ThreadResponse struct {
+	PostId         string  `json:"id"`
+	ReplyCount     int64   `json:"reply_count"`
+	LastReplyAt    int64   `json:"last_reply_at"`
+	LastViewedAt   int64   `json:"last_viewed_at"`
+	Participants   []*User `json:"participants"`
+	Post           *Post   `json:"post"`
+	UnreadReplies  int64   `json:"unread_replies"`
+	UnreadMentions int64   `json:"unread_mentions"`
+	IsUrgent       bool    `json:"is_urgent"`
+	DeleteAt       int64   `json:"delete_at"`
+}
+
+type Threads struct {
+	Total                     int64             `json:"total"`
+	TotalUnreadThreads        int64             `json:"total_unread_threads"`
+	TotalUnreadMentions       int64             `json:"total_unread_mentions"`
+	TotalUnreadUrgentMentions int64             `json:"total_unread_urgent_mentions"`
+	Threads                   []*ThreadResponse `json:"threads"`
+}
+
+type GetUserThreadsOpts struct {
+	// PageSize specifies the size of the returned chunk of results. Default = 30
+	PageSize uint64
+
+	// Extended will enrich the response with participant details. Default = false
+	Extended bool
+
+	// Deleted will specify that even deleted threads should be returned (For mobile sync). Default = false
+	Deleted bool
+
+	// Since filters the threads based on their LastUpdateAt timestamp.
+	Since uint64
+
+	// Before specifies thread id as a cursor for pagination and will return `PageSize` threads before the cursor
+	Before string
+
+	// After specifies thread id as a cursor for pagination and will return `PageSize` threads after the cursor
+	After string
+
+	// Unread will make sure that only threads with unread replies are returned
+	Unread bool
+
+	// TotalsOnly will not fetch any threads and just fetch the total counts
+	TotalsOnly bool
+
+	// ThreadsOnly will fetch threads but not calculate totals and will return 0
+	ThreadsOnly bool
+
+	// TeamOnly will only fetch threads and unreads for the specified team and excludes DMs/GMs
+	TeamOnly bool
+
+	// IncludeIsUrgent will return IsUrgent field as well to assert is the thread is urgent or not
+	IncludeIsUrgent bool
+}
+
+func (o *Thread) Etag() string {
+	return Etag(o.PostId, o.LastReplyAt)
+}
+
+// ThreadMembership models the relationship between a user and a thread of posts, with a similar
+// data structure as ChannelMembership.
+type ThreadMembership struct {
+	// PostId is the root post id of the thread in question.
+	PostId string `json:"post_id"`
+
+	// UserId is the user whose membership in the thread is being tracked.
+	UserId string `json:"user_id"`
+
+	// Following tracks whether the user is following the given thread. This defaults to true
+	// when a ThreadMembership record is created (a record doesn't exist until the user first
+	// starts following the thread), but the user can stop following or resume following at
+	// will.
+	Following bool `json:"following"`
+
+	// LastUpdated is either the creation time of the membership record, or the last time the
+	// membership record was changed (e.g. started/stopped following, viewed thread, mention
+	// count change).
+	//
+	// This field is used to constrain queries of thread memberships to those updated after
+	// a given timestamp (e.g. on websocket reconnect). It's also used as the time column for
+	// deletion decisions during any configured retention policy.
+	LastUpdated int64 `json:"last_update_at"`
+
+	// LastViewed is the last time the user viewed this thread. It is the thread analogue to
+	// the ChannelMembership's LastViewedAt and is used to decide when there are new replies
+	// for the user and where the user should start reading.
+	LastViewed int64 `json:"last_view_at"`
+
+	// UnreadMentions is the number of unseen at-mentions for the user in the given thread. It
+	// is the thread analogue to the ChannelMembership's MentionCount, and is used to highlight
+	// threads with the mention count.
+	UnreadMentions int64 `json:"unread_mentions"`
+}