Add API for Issue set Subscription (#8729)

* add issue subscriber API

* subscribers return []user.APIFormat

* add comments

* more meaningfull description

* without "reqToken()" api works ...
 * should be still secure beause ctx.user has to be there or nothing will hapen

* FIX: getIssueWatchers() get only aktive suscriber

* add return avter error on right position

* Revert "FIX: getIssueWatchers() get only aktive suscriber"

This reverts commit 5eca9291858a821981992b0aaa38cef610d84bca.

* Update routers/api/v1/repo/issue.go

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* test go linter again

* update swagger

* GetIssueWatchers -> GetIssueSubscribers

part one

Co-Authored-By: guillep2k <18600385+guillep2k@users.noreply.github.com>

* GetIssueWatchers -> GetIssueSubscribers
part two

* Revert "test go linter again"

This reverts commit bab12356227e44334de113b76f12099de0b8aaa6.

* change description for unsubscribe too

* golangci-lint timeout avter 5min

* move issueSubscription to seperate file

* dont create black entitys

* use IsWatching until refactoring

* Update License Info

* better swagger description

* Update .golangci.yml

because functions moved from issue.go to issue_subscription.go

* add IssueWatchList type

* batch tasks

* use e Engien

* add error handling

* error should be the last type when returning multiple items

* short version

* reurn empy UserList instead of nil

2 files changed, 41 insertions, 2 deletions

diff --git a/models/issue_watch.go b/models/issue_watch.go
index 2f55c6a84d..1ae0c9d474 100644
--- a/models/issue_watch.go
+++ b/models/issue_watch.go
@@ -16,6 +16,9 @@ type IssueWatch struct {
 	UpdatedUnix timeutil.TimeStamp `xorm:"updated NOT NULL"`
 }
 
+// IssueWatchList contains IssueWatch
+type IssueWatchList []*IssueWatch
+
 // CreateOrUpdateIssueWatch set watching for a user and issue
 func CreateOrUpdateIssueWatch(userID, issueID int64, isWatching bool) error {
 	iw, exists, err := getIssueWatch(x, userID, issueID)
@@ -58,11 +61,11 @@ func getIssueWatch(e Engine, userID, issueID int64) (iw *IssueWatch, exists bool
 }
 
 // GetIssueWatchers returns watchers/unwatchers of a given issue
-func GetIssueWatchers(issueID int64) ([]*IssueWatch, error) {
+func GetIssueWatchers(issueID int64) (IssueWatchList, error) {
 	return getIssueWatchers(x, issueID)
 }
 
-func getIssueWatchers(e Engine, issueID int64) (watches []*IssueWatch, err error) {
+func getIssueWatchers(e Engine, issueID int64) (watches IssueWatchList, err error) {
 	err = e.
 		Where("`issue_watch`.issue_id = ?", issueID).
 		And("`user`.is_active = ?", true).
@@ -83,3 +86,29 @@ func removeIssueWatchersByRepoID(e Engine, userID int64, repoID int64) error {
 		Update(iw)
 	return err
 }
+
+// LoadWatchUsers return watching users
+func (iwl IssueWatchList) LoadWatchUsers() (users UserList, err error) {
+	return iwl.loadWatchUsers(x)
+}
+
+func (iwl IssueWatchList) loadWatchUsers(e Engine) (users UserList, err error) {
+	if len(iwl) == 0 {
+		return []*User{}, nil
+	}
+
+	var userIDs = make([]int64, 0, len(iwl))
+	for _, iw := range iwl {
+		if iw.IsWatching {
+			userIDs = append(userIDs, iw.UserID)
+		}
+	}
+
+	if len(userIDs) == 0 {
+		return []*User{}, nil
+	}
+
+	err = e.In("id", userIDs).Find(&users)
+
+	return
+}
diff --git a/models/userlist.go b/models/userlist.go
index a2a4248482..16ec6fee55 100644
--- a/models/userlist.go
+++ b/models/userlist.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	"code.gitea.io/gitea/modules/log"
+	api "code.gitea.io/gitea/modules/structs"
 )
 
 //UserList is a list of user.
@@ -93,3 +94,12 @@ func (users UserList) loadTwoFactorStatus(e Engine) (map[int64]*TwoFactor, error
 	}
 	return tokenMaps, nil
 }
+
+//APIFormat return list of users in api format
+func (users UserList) APIFormat() []*api.User {
+	var result []*api.User
+	for _, u := range users {
+		result = append(result, u.APIFormat())
+	}
+	return result
+}