[MM-25659] ability to permanent delete channel through client (#15202)

Summary

    Ability to permanent delete channel through client

Ticket Link

    https://mattermost.atlassian.net/browse/MM-25659

model/client4.go

@@ -2562,6 +2562,16 @@ func (c *Client4) DeleteChannel(channelId string) (bool, *Response) {
 	return CheckStatusOK(r), BuildResponse(r)
 }
 
+// PermanentDeleteChannel deletes a channel based on the provided channel id string.
+func (c *Client4) PermanentDeleteChannel(channelId string) (bool, *Response) {
+	r, err := c.DoApiDelete(c.GetChannelRoute(channelId) + "?permanent=" + c.boolString(true))
+	if err != nil {
+		return false, BuildErrorResponse(r, err)
+	}
+	defer closeBody(r)
+	return CheckStatusOK(r), BuildResponse(r)
+}
+
 // MoveChannel moves the channel to the destination team.
 func (c *Client4) MoveChannel(channelId, teamId string, force bool) (*Channel, *Response) {
 	requestBody := map[string]interface{}{

model/config.go

@@ -329,6 +329,7 @@ type ServiceSettings struct {
 	DEPRECATED_DO_NOT_USE_ImageProxyOptions           *string `json:"ImageProxyOptions" mapstructure:"ImageProxyOptions"` // This field is deprecated and must not be used.
 	EnableAPITeamDeletion                             *bool
 	EnableAPIUserDeletion                             *bool
+	EnableAPIChannelDeletion                          *bool
 	ExperimentalEnableHardenedMode                    *bool
 	DisableLegacyMFA                                  *bool `restricted:"true"`
 	ExperimentalStrictCSRFEnforcement                 *bool `restricted:"true"`
@@ -705,6 +706,10 @@ func (s *ServiceSettings) SetDefaults(isUpdate bool) {
 		s.EnableAPIUserDeletion = NewBool(false)
 	}
 
+	if s.EnableAPIChannelDeletion == nil {
+		s.EnableAPIChannelDeletion = NewBool(false)
+	}
+
 	if s.ExperimentalEnableHardenedMode == nil {
 		s.ExperimentalEnableHardenedMode = NewBool(false)
 	}