Correct swagger annotations for enums, status codes, and notification state (#37030)

## ⚠️ BREAKING ⚠️

- delete reaction endpoints is changed to return 204 No Content rather
than 200 with no content.

## Summary

Add swagger:enum annotations and migrate all enum comments from the
deprecated comma-separated format to JSON arrays. Introduce
NotifySubjectStateType with open/closed/merged values. Fix delete
reaction endpoints to return 204 instead of 200.

modules/structs/issue.go

@@ -14,6 +14,8 @@ import (
 )
 
 // StateType issue state type
+//
+// swagger:enum StateType
 type StateType string
 
 const (
@@ -21,10 +23,11 @@ const (
 	StateOpen StateType = "open"
 	// StateClosed pr is closed
 	StateClosed StateType = "closed"
-	// StateAll is all
-	StateAll StateType = "all"
 )
 
+// StateAll is a query parameter filter value, not a valid object state.
+const StateAll = "all"
+
 // PullRequestMeta PR info if an issue is a PR
 type PullRequestMeta struct {
 	HasMerged        bool       `json:"merged"`
@@ -58,15 +61,11 @@ type Issue struct {
 	Labels           []*Label      `json:"labels"`
 	Milestone        *Milestone    `json:"milestone"`
 	// deprecated
-	Assignee  *User   `json:"assignee"`
-	Assignees []*User `json:"assignees"`
-	// Whether the issue is open or closed
-	//
-	// type: string
-	// enum: open,closed
-	State    StateType `json:"state"`
-	IsLocked bool      `json:"is_locked"`
-	Comments int       `json:"comments"`
+	Assignee  *User     `json:"assignee"`
+	Assignees []*User   `json:"assignees"`
+	State     StateType `json:"state"`
+	IsLocked  bool      `json:"is_locked"`
+	Comments  int       `json:"comments"`
 	// swagger:strfmt date-time
 	Created time.Time `json:"created_at"`
 	// swagger:strfmt date-time
@@ -132,6 +131,8 @@ type IssueDeadline struct {
 }
 
 // IssueFormFieldType defines issue form field type, can be "markdown", "textarea", "input", "dropdown" or "checkboxes"
+//
+// swagger:enum IssueFormFieldType
 type IssueFormFieldType string
 
 const (
@@ -168,7 +169,8 @@ func (iff IssueFormField) VisibleInContent() bool {
 }
 
 // IssueFormFieldVisible defines issue form field visible
-// swagger:model
+//
+// swagger:enum IssueFormFieldVisible
 type IssueFormFieldVisible string
 
 const (