microsoft: Support setting the prompt type

Signed-off-by: Erica Taylor <ricky@wellplayed.games>

connector/microsoft/microsoft.go

@@ -53,6 +53,10 @@ type Config struct {
 	GroupNameFormat      GroupNameFormat `json:"groupNameFormat"`
 	UseGroupsAsWhitelist bool            `json:"useGroupsAsWhitelist"`
 	EmailToLowercase     bool            `json:"emailToLowercase"`
+
+	// PromptType is used for the prompt query parameter.
+	// For valid values, see https://docs.microsoft.com/en-us/azure/active-directory/develop/v2-oauth2-auth-code-flow#request-an-authorization-code.
+	PromptType string `json:"promptType"`
 }
 
 // Open returns a strategy for logging in through Microsoft.
@@ -70,6 +74,7 @@ func (c *Config) Open(id string, logger log.Logger) (connector.Connector, error)
 		useGroupsAsWhitelist: c.UseGroupsAsWhitelist,
 		logger:               logger,
 		emailToLowercase:     c.EmailToLowercase,
+		promptType:           c.PromptType,
 	}
 	// By default allow logins from both personal and business/school
 	// accounts.
@@ -113,6 +118,7 @@ type microsoftConnector struct {
 	useGroupsAsWhitelist bool
 	logger               log.Logger
 	emailToLowercase     bool
+	promptType           string
 }
 
 func (c *microsoftConnector) isOrgTenant() bool {
@@ -150,7 +156,12 @@ func (c *microsoftConnector) LoginURL(scopes connector.Scopes, callbackURL, stat
 		return "", fmt.Errorf("expected callback URL %q did not match the URL in the config %q", callbackURL, c.redirectURI)
 	}
 
-	return c.oauth2Config(scopes).AuthCodeURL(state), nil
+	var options []oauth2.AuthCodeOption
+	if c.promptType != "" {
+		options = append(options, oauth2.SetAuthURLParam("prompt", c.promptType))
+	}
+
+	return c.oauth2Config(scopes).AuthCodeURL(state, options...), nil
 }
 
 func (c *microsoftConnector) HandleCallback(s connector.Scopes, r *http.Request) (identity connector.Identity, err error) {