feat: add basic structure of idp templates (#5053)

add basic structure and implement first providers for IDP templates to be able to manage and use them in the future

internal/idp/providers/oauth/session.go

@@ -0,0 +1,63 @@
+package oauth
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	"github.com/zitadel/oidc/v2/pkg/client/rp"
+	httphelper "github.com/zitadel/oidc/v2/pkg/http"
+	"github.com/zitadel/oidc/v2/pkg/oidc"
+
+	"github.com/zitadel/zitadel/internal/idp"
+)
+
+var ErrCodeMissing = errors.New("no auth code provided")
+
+var _ idp.Session = (*Session)(nil)
+
+// Session is the [idp.Session] implementation for the OAuth2.0 provider.
+type Session struct {
+	AuthURL string
+	Code    string
+	Tokens  *oidc.Tokens
+
+	Provider *Provider
+}
+
+// GetAuthURL implements the [idp.Session] interface.
+func (s *Session) GetAuthURL() string {
+	return s.AuthURL
+}
+
+// FetchUser implements the [idp.Session] interface.
+// It will execute an OAuth 2.0 code exchange if needed to retrieve the access token,
+// call the specified userEndpoint and map the received information into an [idp.User].
+func (s *Session) FetchUser(ctx context.Context) (user idp.User, err error) {
+	if s.Tokens == nil {
+		if err = s.authorize(ctx); err != nil {
+			return nil, err
+		}
+	}
+	req, err := http.NewRequest("GET", s.Provider.userEndpoint, nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("authorization", s.Tokens.TokenType+" "+s.Tokens.AccessToken)
+	mapper := s.Provider.userMapper()
+	if err := httphelper.HttpRequest(s.Provider.RelyingParty.HttpClient(), req, &mapper); err != nil {
+		return nil, err
+	}
+	return mapper, nil
+}
+
+func (s *Session) authorize(ctx context.Context) (err error) {
+	if s.Code == "" {
+		return ErrCodeMissing
+	}
+	s.Tokens, err = rp.CodeExchange(ctx, s.Code, s.Provider.RelyingParty)
+	if err != nil {
+		return err
+	}
+	return nil
+}