Add user:pass Basic auth mode for API-key connectors

The API-key connection transport could present a key as a Bearer token,
an x-api-key header, a custom scheme (SSWS/Token), or HTTP Basic with an
empty password (Cursor). None of these can carry a real password, which
providers such as ClickHouse Cloud (keyId:keySecret) and Langfuse
(publicKey:secretKey) require.

Add a fourth mode, APIKeyBasicAuthUserPass, that base64-encodes the
stored "username:password" credential verbatim into Authorization: Basic.
SetBasicAuth cannot express this -- it re-appends a ":" and corrupts the
credential. The mode is wired generically through the registry and the
create-connector resolver and is mutually exclusive with the other
API-key auth modes.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/registry.go

@@ -71,16 +71,21 @@ func (r *Registry) Register(reg *Registration) error {
 		return fmt.Errorf("cannot register connector provider %q: missing DisplayName", reg.Provider)
 	}
 
-	// APIKeyBasicAuth, APIKeyHeader, and APIKeyAuthScheme select different
-	// presentations of the same key; setting more than one is a programmer
-	// error with a silent winner (Client checks BasicAuth, then Header,
-	// then Scheme). Reject it at startup.
+	// APIKeyBasicAuth, APIKeyBasicAuthUserPass, APIKeyHeader, and
+	// APIKeyAuthScheme select different presentations of the same key;
+	// setting more than one is a programmer error with a silent winner
+	// (Client checks BasicAuth, then BasicAuthUserPass, then Header, then
+	// Scheme). Reject it at startup.
 	apiKeyModes := 0
 
 	if reg.APIKeyBasicAuth {
 		apiKeyModes++
 	}
 
+	if reg.APIKeyBasicAuthUserPass {
+		apiKeyModes++
+	}
+
 	if reg.APIKeyHeader != "" {
 		apiKeyModes++
 	}
@@ -90,7 +95,7 @@ func (r *Registry) Register(reg *Registration) error {
 	}
 
 	if apiKeyModes > 1 {
-		return fmt.Errorf("cannot register connector provider %q: APIKeyBasicAuth, APIKeyHeader, and APIKeyAuthScheme are mutually exclusive", reg.Provider)
+		return fmt.Errorf("cannot register connector provider %q: APIKeyBasicAuth, APIKeyBasicAuthUserPass, APIKeyHeader, and APIKeyAuthScheme are mutually exclusive", reg.Provider)
 	}
 
 	// BuildTokenURLForDomain and BuildTokenURLForSite both build the token
@@ -206,6 +211,19 @@ func (r *Registry) APIKeyAuthScheme(p coredata.ConnectorProvider) string {
 	return ""
 }
 
+// APIKeyUsesBasicAuthUserPass reports whether an API-key connection for the
+// given provider must present its key as a complete HTTP Basic credential
+// (`username:password` already encoded in the key, base64'd verbatim)
+// instead of a Bearer token. Returns false for unknown providers and for
+// providers that use the default Bearer scheme.
+func (r *Registry) APIKeyUsesBasicAuthUserPass(p coredata.ConnectorProvider) bool {
+	if reg, ok := r.Get(p); ok {
+		return reg.APIKeyBasicAuthUserPass
+	}
+
+	return false
+}
+
 // ProviderOAuth2Scopes returns the OAuth2 scopes the access review
 // driver for the given provider needs to list user accounts. Returns
 // nil for providers that do not need any scopes (Notion, Intercom)

pkg/connector/provider/registry_test.go

@@ -109,6 +109,20 @@ func TestRegistry_Register(t *testing.T) {
 		assert.Contains(t, err.Error(), "mutually exclusive")
 	})
 
+	t.Run("APIKeyBasicAuthUserPass and APIKeyHeader mutually exclusive", func(t *testing.T) {
+		t.Parallel()
+
+		r := provider.NewRegistry()
+		err := r.Register(&provider.Registration{
+			Provider:                coredata.ConnectorProviderSlack,
+			DisplayName:             "Slack",
+			APIKeyBasicAuthUserPass: true,
+			APIKeyHeader:            "x-api-key",
+		})
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "mutually exclusive")
+	})
+
 	t.Run("BuildTokenURLForDomain and BuildTokenURLForSite mutually exclusive", func(t *testing.T) {
 		t.Parallel()
 

pkg/connector/provider/types.go

@@ -103,6 +103,15 @@ type Registration struct {
 	// Consumed when the create-connector resolver builds the
 	// APIKeyConnection.
 	APIKeyAuthScheme string
+	// APIKeyBasicAuthUserPass, when true, presents the API key as a complete
+	// HTTP Basic credential whose `username:password` pair is already
+	// encoded in the key (base64 of the verbatim string) — required by
+	// providers such as ClickHouse Cloud (keyId:keySecret) and Langfuse
+	// (publicKey:secretKey) whose Basic credential carries a real
+	// password, unlike APIKeyBasicAuth's empty-password form. Mutually
+	// exclusive with the other API-key auth modes. Consumed when the
+	// create-connector resolver builds the APIKeyConnection.
+	APIKeyBasicAuthUserPass bool
 
 	// BuildProbeURL derives a per-connector probe URL when the API host or
 	// path depends on connector settings (e.g. a customer subdomain or