Spring security auth configuration for simple api-key header (Kotlin)

spring-security-config-for-api-key-auth.code

            .addFilter(object: AbstractPreAuthenticatedProcessingFilter() {
                override fun getPreAuthenticatedPrincipal(req: HttpServletRequest) = req.getHeader("X-API-KEY") ?: ""
                override fun getPreAuthenticatedCredentials(req: HttpServletRequest) = ""
            }.apply {
                setAuthenticationManager {
                    it.isAuthenticated = it.principal == "{your-api-key}"
                    it
                }
            })