Add access source drivers

Add Driver interface and implementations for Google
Workspace, Linear, Slack, 1Password, HubSpot, DocuSign,
Notion, Brex, Tally, Cloudflare, CSV, Probo memberships,
Sentry, OpenAI, Supabase, GitHub, Intercom, and Resend.
Include name resolvers, VCR test infrastructure with
cassettes, and RFC 5988 link header parser.

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

pkg/accessreview/drivers/google_workspace.go

@@ -0,0 +1,157 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.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 drivers
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	admin "google.golang.org/api/admin/directory/v1"
+	"google.golang.org/api/option"
+
+	"go.probo.inc/probo/pkg/coredata"
+)
+
+// GoogleWorkspaceDriver fetches user accounts from Google Workspace
+// using the Admin Directory API via an OAuth2-authenticated HTTP client.
+type GoogleWorkspaceDriver struct {
+	httpClient *http.Client
+}
+
+func NewGoogleWorkspaceDriver(httpClient *http.Client) *GoogleWorkspaceDriver {
+	return &GoogleWorkspaceDriver{
+		httpClient: &http.Client{
+			Transport: &retryRoundTripper{
+				next:       httpClient.Transport,
+				maxRetries: 3,
+			},
+		},
+	}
+}
+
+// retryRoundTripper retries requests that receive 5xx or 429 responses
+// with exponential backoff.
+type retryRoundTripper struct {
+	next       http.RoundTripper
+	maxRetries int
+}
+
+func (rt *retryRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	transport := rt.next
+	if transport == nil {
+		transport = http.DefaultTransport
+	}
+
+	var lastResp *http.Response
+	for attempt := range rt.maxRetries {
+		resp, err := transport.RoundTrip(req)
+		if err != nil {
+			return nil, err
+		}
+
+		if resp.StatusCode != http.StatusTooManyRequests && resp.StatusCode < 500 {
+			return resp, nil
+		}
+
+		_ = resp.Body.Close()
+		lastResp = resp
+
+		backoff := time.Duration(250*(1<<attempt)) * time.Millisecond
+		select {
+		case <-req.Context().Done():
+			return nil, req.Context().Err()
+		case <-time.After(backoff):
+		}
+	}
+
+	return lastResp, nil
+}
+
+func (d *GoogleWorkspaceDriver) ListAccounts(ctx context.Context) ([]AccountRecord, error) {
+	adminService, err := admin.NewService(ctx, option.WithHTTPClient(d.httpClient))
+	if err != nil {
+		return nil, fmt.Errorf("cannot create google admin service: %w", err)
+	}
+
+	var records []AccountRecord
+	pageToken := ""
+
+	for range maxPaginationPages {
+		call := adminService.Users.List().
+			Customer("my_customer").
+			MaxResults(500).
+			Projection("full").
+			Context(ctx)
+		if pageToken != "" {
+			call = call.PageToken(pageToken)
+		}
+
+		resp, err := call.Do()
+		if err != nil {
+			return nil, fmt.Errorf("cannot list google workspace users: %w", err)
+		}
+
+		for _, u := range resp.Users {
+			rec := AccountRecord{
+				Email:       u.PrimaryEmail,
+				FullName:    u.Name.FullName,
+				Active:      !u.Suspended && !u.Archived,
+				IsAdmin:     u.IsAdmin,
+				ExternalID:  u.Id,
+				MFAStatus:   coredata.MFAStatusUnknown,
+				AuthMethod:  coredata.AccessEntryAuthMethodSSO,
+				AccountType: coredata.AccessEntryAccountTypeUser,
+			}
+
+			if u.IsEnrolledIn2Sv {
+				rec.MFAStatus = coredata.MFAStatusEnabled
+			} else {
+				rec.MFAStatus = coredata.MFAStatusDisabled
+			}
+
+			if u.CreationTime != "" {
+				if t, err := time.Parse(time.RFC3339, u.CreationTime); err == nil {
+					rec.CreatedAt = &t
+				}
+			}
+
+			if u.LastLoginTime != "" {
+				if t, err := time.Parse(time.RFC3339, u.LastLoginTime); err == nil {
+					rec.LastLogin = &t
+				}
+			}
+
+			switch {
+			case u.IsAdmin:
+				rec.Role = "Super Admin"
+			case u.IsDelegatedAdmin:
+				rec.Role = "Delegated Admin"
+			default:
+				rec.Role = "User"
+			}
+
+			records = append(records, rec)
+		}
+
+		pageToken = resp.NextPageToken
+		if pageToken == "" {
+			return records, nil
+		}
+	}
+
+	return nil, fmt.Errorf("cannot list all google workspace accounts: %w", ErrPaginationLimitReached)
+}