add enable_section option for UserGroup API (#1364)

close #1363 

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##### Should this be an issue instead
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some use case)
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##### API changes

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- no tests, if you're adding to the API include at least a single test
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usergroups.go

@@ -3,6 +3,7 @@ package slack
 import (
 	"context"
 	"net/url"
+	"strconv"
 	"strings"
 )
 
@@ -50,20 +51,45 @@ func (api *Client) userGroupRequest(ctx context.Context, path string, values url
 	return response, response.Err()
 }
 
+// createUserGroupParams contains arguments for CreateUserGroup method call
+type createUserGroupParams struct {
+	enableSection bool
+}
+
+// CreateUserGroupOption options for the CreateUserGroup method call.
+type CreateUserGroupOption func(*createUserGroupParams)
+
+// CreateUserGroupOptionEnableSection enable the section for the user group (default: false)
+func CreateUserGroupOptionEnableSection(enableSection bool) CreateUserGroupOption {
+	return func(params *createUserGroupParams) {
+		params.enableSection = enableSection
+	}
+}
+
 // CreateUserGroup creates a new user group.
 // For more information see the CreateUserGroupContext documentation.
-func (api *Client) CreateUserGroup(userGroup UserGroup) (UserGroup, error) {
-	return api.CreateUserGroupContext(context.Background(), userGroup)
+func (api *Client) CreateUserGroup(userGroup UserGroup, options ...CreateUserGroupOption) (UserGroup, error) {
+	return api.CreateUserGroupContext(context.Background(), userGroup, options...)
 }
 
 // CreateUserGroupContext creates a new user group with a custom context.
 // Slack API docs: https://api.slack.com/methods/usergroups.create
-func (api *Client) CreateUserGroupContext(ctx context.Context, userGroup UserGroup) (UserGroup, error) {
+func (api *Client) CreateUserGroupContext(ctx context.Context, userGroup UserGroup, options ...CreateUserGroupOption) (UserGroup, error) {
+	params := createUserGroupParams{}
+
+	for _, opt := range options {
+		opt(&params)
+	}
+
 	values := url.Values{
 		"token": {api.token},
 		"name":  {userGroup.Name},
 	}
 
+	if params.enableSection {
+		values["enable_section"] = []string{strconv.FormatBool(params.enableSection)}
+	}
+
 	if userGroup.TeamID != "" {
 		values["team_id"] = []string{userGroup.TeamID}
 	}
@@ -236,12 +262,20 @@ func UpdateUserGroupsOptionChannels(channels []string) UpdateUserGroupsOption {
 	}
 }
 
+// UpdateUserGroupsOptionEnableSection enable the section for the user group (default: false)
+func UpdateUserGroupsOptionEnableSection(enableSection bool) UpdateUserGroupsOption {
+	return func(params *UpdateUserGroupsParams) {
+		params.EnableSection = enableSection
+	}
+}
+
 // UpdateUserGroupsParams contains arguments for UpdateUserGroup method call
 type UpdateUserGroupsParams struct {
-	Name        string
-	Handle      string
-	Description *string
-	Channels    *[]string
+	Name          string
+	Handle        string
+	Description   *string
+	Channels      *[]string
+	EnableSection bool
 }
 
 // UpdateUserGroup will update an existing user group.
@@ -280,6 +314,10 @@ func (api *Client) UpdateUserGroupContext(ctx context.Context, userGroupID strin
 		values["channels"] = []string{strings.Join(*params.Channels, ",")}
 	}
 
+	if params.EnableSection {
+		values["enable_section"] = []string{strconv.FormatBool(params.EnableSection)}
+	}
+
 	response, err := api.userGroupRequest(ctx, "usergroups.update", values)
 	if err != nil {
 		return UserGroup{}, err