Add five API-key access-review connectors

Add Mercury, Apollo.io, Deepgram, ClickHouse Cloud, and Langfuse as
access-review connectors. All are API-key, single-tenant providers
(Pattern 3): the key identifies one tenant, so there is no OAuth flow,
picker UI, or bootstrap/helm configuration.

- Mercury: Bearer token, GET /api/v1/users, cursor pagination.
- Apollo.io: x-api-key header, GET /api/v1/users/search (teammates).
- Deepgram: Token scheme; lists members across every project and
  dedupes by member_id, unioning per-project scopes.
- ClickHouse Cloud: HTTP Basic (keyId:keySecret); discovers the org
  via GET /v1/organizations, then lists its members.
- Langfuse: HTTP Basic (publicKey:secretKey); a base-URL setting
  selects the regional cloud host or a self-hosted instance.

Each adds the enum value, migration, GraphQL binding, provider
Registration, a driver with a cassette-driven test, and a brand logo.

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

pkg/connector/provider/mercury.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2026 Probo Inc <hello@probo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package provider
+
+import (
+	"context"
+	"net/http"
+
+	"go.gearno.de/kit/log"
+	"go.probo.inc/probo/pkg/accessreview/drivers"
+	"go.probo.inc/probo/pkg/coredata"
+)
+
+func mercuryRegistration() *Registration {
+	return &Registration{
+		Provider:       coredata.ConnectorProviderMercury,
+		DisplayName:    "Mercury",
+		SupportsAPIKey: true,
+		// Mercury authenticates with a self-serve API token presented as
+		// Authorization: Bearer, the default APIKeyConnection scheme. There
+		// is no third-party OAuth2 flow for the Users API. The token is
+		// bound to one Mercury organization, so there is nothing to pick
+		// (Pattern 3): no settings struct, no picker, no
+		// SetOrganizationSettings.
+		//
+		// ProbeURL lets the connection-status check confirm the token is
+		// live with a lightweight GET; the transport attaches the Bearer
+		// token and a dead token returns 401/403.
+		ProbeURL: "https://api.mercury.com/api/v1/users?limit=1",
+		//
+		// No NewNameResolver: GET /api/v1/users carries no organization
+		// name and a read-only token may lack other scopes, so the source
+		// keeps its generic name (the source-name worker degrades
+		// gracefully).
+		NewDriver: func(_ context.Context, c *http.Client, _ *coredata.Connector, _ *log.Logger) (drivers.Driver, error) {
+			return drivers.NewMercuryDriver(c), nil
+		},
+	}
+}