feat(eventstore): increase parallel write capabilities (#5940)

This implementation increases parallel write capabilities of the eventstore.
Please have a look at the technical advisories: [05](https://zitadel.com/docs/support/advisory/a10005) and  [06](https://zitadel.com/docs/support/advisory/a10006).
The implementation of eventstore.push is rewritten and stored events are migrated to a new table `eventstore.events2`.
If you are using cockroach: make sure that the database user of ZITADEL has `VIEWACTIVITY` grant. This is used to query events.

internal/database/dialect/config.go

@@ -6,11 +6,6 @@ import (
 	"time"
 )
 
-type Config struct {
-	Dialects map[string]interface{} `mapstructure:",remain"`
-	Dialect  Matcher
-}
-
 type Dialect struct {
 	Matcher   Matcher
 	Config    Connector
@@ -29,7 +24,7 @@ type Matcher interface {
 }
 
 type Connector interface {
-	Connect(useAdmin bool) (*sql.DB, error)
+	Connect(useAdmin, isEventPusher bool, pusherRatio float32, appName string) (*sql.DB, error)
 	Password() string
 	Database
 }

internal/database/dialect/connections.go

@@ -0,0 +1,39 @@
+package dialect
+
+import "errors"
+
+type ConnectionInfo struct {
+	EventstorePusher ConnectionConfig
+	ZITADEL          ConnectionConfig
+}
+
+type ConnectionConfig struct {
+	MaxOpenConns,
+	MaxIdleConns uint32
+}
+
+func NewConnectionInfo(openConns, idleConns uint32, pusherRatio float64) (*ConnectionInfo, error) {
+	if pusherRatio < 0 || pusherRatio > 1 {
+		return nil, errors.New("EventPushConnRatio must be between 0 and 1")
+	}
+	if openConns < 2 {
+		return nil, errors.New("MaxOpenConns of the database must be higher that 1")
+	}
+
+	info := new(ConnectionInfo)
+
+	info.EventstorePusher.MaxOpenConns = uint32(pusherRatio * float64(openConns))
+	info.EventstorePusher.MaxIdleConns = uint32(pusherRatio * float64(idleConns))
+
+	if info.EventstorePusher.MaxOpenConns < 1 && pusherRatio > 0 {
+		info.EventstorePusher.MaxOpenConns = 1
+	}
+	if info.EventstorePusher.MaxIdleConns < 1 && pusherRatio > 0 {
+		info.EventstorePusher.MaxIdleConns = 1
+	}
+
+	info.ZITADEL.MaxOpenConns = openConns - info.EventstorePusher.MaxOpenConns
+	info.ZITADEL.MaxIdleConns = idleConns - info.EventstorePusher.MaxIdleConns
+
+	return info, nil
+}