✨️ Do not block middleware startup due to stream intialization (#281)

* 🍱 not block on stream startup

* 🍱 fix

* 🍱 fix lint

* 🍱 fix lint

* 🍱 fix lint

* 🍱 update readme

* 📚 clarify StreamStartupBlock warning in README

Make the fail-open implication of StreamStartupBlock=false explicit:
banned IPs are allowed through until the first stream sync completes.

* 🐛 clear isCrowdsecStreamStartup on alreadyUpdated path

When cacheTimeoutKey is already set (another instance/process has
populated the stream cache within the update window), the early return
in handleStreamCache used to leave isCrowdsecStreamStartup at true,
causing this instance to keep sending startup=true on subsequent ticks.
Flip the flag in the early-return path so startup is correctly tracked
across multi-instance deployments sharing a cache.

---------

Co-authored-by: mhx <mathieu@hanotaux.fr>

pkg/configuration/configuration.go

@@ -84,6 +84,7 @@ type Config struct {
 	UpdateIntervalSeconds                      int64    `json:"updateIntervalSeconds,omitempty"`
 	MetricsUpdateIntervalSeconds               int64    `json:"metricsUpdateIntervalSeconds,omitempty"`
 	UpdateMaxFailure                           int64    `json:"updateMaxFailure,omitempty"`
+	StreamStartupBlock                         bool     `json:"streamStartupBlock,omitempty"`
 	DefaultDecisionSeconds                     int64    `json:"defaultDecisionSeconds,omitempty"`
 	RemediationStatusCode                      int      `json:"remediationStatusCode,omitempty"`
 	HTTPTimeoutSeconds                         int64    `json:"httpTimeoutSeconds,omitempty"`
@@ -146,6 +147,7 @@ func New() *Config {
 		UpdateIntervalSeconds:           60,
 		MetricsUpdateIntervalSeconds:    600,
 		UpdateMaxFailure:                0,
+		StreamStartupBlock:              true,
 		DefaultDecisionSeconds:          60,
 		RemediationStatusCode:           http.StatusForbidden,
 		HTTPTimeoutSeconds:              10,