Refactor sign-in page and IAM service lifecycle

Redesign the sign-in page to show email/password form inline
with OIDC provider buttons (with vendor icons) instead of
separate pages. Extract OIDCProvider type to its own file.

Replace errgroup with sync.WaitGroup + WithCancelCause for
graceful shutdown in IAM services. Refactor garbage collectors
to use functional options and time.Ticker instead of
time.After to avoid repeated allocations.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/iam/saml/gc.go

@@ -34,20 +34,36 @@ type (
 		interval time.Duration
 		logger   *log.Logger
 	}
+
+	GarbageCollectorOption func(*GarbageCollector)
 )
 
-func NewGarbageCollector(
-	pg *pg.Client,
-	interval time.Duration,
-	logger *log.Logger,
-) *GarbageCollector {
-	return &GarbageCollector{
-		pg:       pg,
-		interval: interval,
-		logger:   logger.Named("saml.garbage_collector").With(log.Duration("interval", interval)),
+func WithGarbageCollectionInterval(interval time.Duration) GarbageCollectorOption {
+	return func(gc *GarbageCollector) {
+		gc.interval = interval
 	}
 }
 
+func NewGarbageCollector(
+	pgClient *pg.Client,
+	logger *log.Logger,
+	opts ...GarbageCollectorOption,
+) *GarbageCollector {
+	gc := &GarbageCollector{
+		pg:       pgClient,
+		interval: DefaultGarbageCollectionInterval,
+		logger:   logger.Named("saml.garbage_collector"),
+	}
+
+	for _, opt := range opts {
+		opt(gc)
+	}
+
+	gc.logger = gc.logger.With(log.Duration("interval", gc.interval))
+
+	return gc
+}
+
 func (gc *GarbageCollector) Run(ctx context.Context) error {
 	gc.logger.InfoCtx(ctx, "saml garbage collector starting")
 
@@ -55,12 +71,15 @@ func (gc *GarbageCollector) Run(ctx context.Context) error {
 		gc.logger.ErrorCtx(ctx, "cannot run initial cleanup", log.Error(err))
 	}
 
+	ticker := time.NewTicker(gc.interval)
+	defer ticker.Stop()
+
 	for {
 		select {
 		case <-ctx.Done():
 			gc.logger.InfoCtx(ctx, "saml garbage collector shutting down")
 			return ctx.Err()
-		case <-time.After(gc.interval):
+		case <-ticker.C:
 			if err := gc.cleanup(ctx); err != nil {
 				gc.logger.ErrorCtx(ctx, "cannot run periodic cleanup", log.Error(err))
 			}