Add openai codex support

internal/auth/codex/openai.go

@@ -0,0 +1,36 @@
+package codex
+
+// PKCECodes holds PKCE verification codes for OAuth2 PKCE flow
+type PKCECodes struct {
+	// CodeVerifier is the cryptographically random string used to correlate
+	// the authorization request to the token request
+	CodeVerifier string `json:"code_verifier"`
+	// CodeChallenge is the SHA256 hash of the code verifier, base64url-encoded
+	CodeChallenge string `json:"code_challenge"`
+}
+
+// CodexTokenData holds OAuth token information from OpenAI
+type CodexTokenData struct {
+	// IDToken is the JWT ID token containing user claims
+	IDToken string `json:"id_token"`
+	// AccessToken is the OAuth2 access token for API access
+	AccessToken string `json:"access_token"`
+	// RefreshToken is used to obtain new access tokens
+	RefreshToken string `json:"refresh_token"`
+	// AccountID is the OpenAI account identifier
+	AccountID string `json:"account_id"`
+	// Email is the OpenAI account email
+	Email string `json:"email"`
+	// Expire is the timestamp of the token expire
+	Expire string `json:"expired"`
+}
+
+// CodexAuthBundle aggregates authentication data after OAuth flow completion
+type CodexAuthBundle struct {
+	// APIKey is the OpenAI API key obtained from token exchange
+	APIKey string `json:"api_key"`
+	// TokenData contains the OAuth tokens from the authentication flow
+	TokenData CodexTokenData `json:"token_data"`
+	// LastRefresh is the timestamp of the last token refresh
+	LastRefresh string `json:"last_refresh"`
+}