v5.5.2

Improvements:

• added <memcachedSessionManager cookiePrefix="..."/> to support multiple Membrane instances using MemcacheD as session storage
• added <flowInitiator logoutBeforeFlow="true" /> attribute
• added <openapi> response header validation

Fixes:

• upgraded several dependencies
• fixed some examples using external services
• fixed <openapi><rewrite> logic
• fixed <openapi> response validation with status code 204