feat: Allow the use of a custom discovery endpoint (#152)

* Allow the use of custom endpoints

* Remove the custom constrtouctor and replace with an optional argument to override the discovery endpoit

pkg/client/client.go

@@ -26,8 +26,13 @@ var (
 )
 
 //Discover calls the discovery endpoint of the provided issuer and returns its configuration
-func Discover(issuer string, httpClient *http.Client) (*oidc.DiscoveryConfiguration, error) {
+//It accepts an optional argument "wellknownUrl" which can be used to overide the dicovery endpoint url
+func Discover(issuer string, httpClient *http.Client, wellKnownUrl ...string) (*oidc.DiscoveryConfiguration, error) {
+
 	wellKnown := strings.TrimSuffix(issuer, "/") + oidc.DiscoveryEndpoint
+	if len(wellKnownUrl) == 1 && wellKnownUrl[0] != "" {
+		wellKnown = wellKnownUrl[0]
+	}
 	req, err := http.NewRequest("GET", wellKnown, nil)
 	if err != nil {
 		return nil, err

pkg/client/rp/relaying_party.go

@@ -69,11 +69,12 @@ var (
 )
 
 type relyingParty struct {
-	issuer      string
-	endpoints   Endpoints
-	oauthConfig *oauth2.Config
-	oauth2Only  bool
-	pkce        bool
+	issuer            string
+	DiscoveryEndpoint string
+	endpoints         Endpoints
+	oauthConfig       *oauth2.Config
+	oauth2Only        bool
+	pkce              bool
 
 	httpClient    *http.Client
 	cookieHandler *httphelper.CookieHandler
@@ -170,7 +171,7 @@ func NewRelyingPartyOIDC(issuer, clientID, clientSecret, redirectURI string, sco
 			return nil, err
 		}
 	}
-	discoveryConfiguration, err := client.Discover(rp.issuer, rp.httpClient)
+	discoveryConfiguration, err := client.Discover(rp.issuer, rp.httpClient, rp.DiscoveryEndpoint)
 	if err != nil {
 		return nil, err
 	}
@@ -184,6 +185,13 @@ func NewRelyingPartyOIDC(issuer, clientID, clientSecret, redirectURI string, sco
 //Option is the type for providing dynamic options to the relyingParty
 type Option func(*relyingParty) error
 
+func WithCustomDiscoveryUrl(url string) Option {
+	return func(rp *relyingParty) error {
+		rp.DiscoveryEndpoint = url
+		return nil
+	}
+}
+
 //WithCookieHandler set a `CookieHandler` for securing the various redirects
 func WithCookieHandler(cookieHandler *httphelper.CookieHandler) Option {
 	return func(rp *relyingParty) error {