Kotlin Extension Functions for ReactiveUserDetailsService

Spring (WebFlux) has e.g. this extension function:

suspend fun ServerResponse.BodyBuilder.bodyValueAndAwait(body: Any): ServerResponse =
        bodyValue(body).awaitSingle()

See https://github.com/spring-projects/spring-framework/blob/master/spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerResponseExtensions.kt#L62

According to the ...AndAwait naming convention I propose these Kotlin extension functions for ReactiveUserDetailsService:

suspend fun ReactiveUserDetailsService.findByUsernameAndAwait(username: String): UserDetails? =
    findByUsername(username).awaitFirstOrNull()

suspend fun ReactiveUserDetailsService.getAuthoritiesAndAwait(username: String): Collection<GrantedAuthority> {
    val userDetails = findByUsernameAndAwait(username) ?: return emptyList()
    return userDetails.authorities
}

suspend fun ReactiveUserDetailsService.getRolesAndAwait(username: String): Collection<String?> =
    getAuthoritiesAndAwait(username).map { grantedAuthority -> grantedAuthority.authority }

Start with ReactiveUserDetailsService and compare the proposed functions with Spring WebFlux's referenced ServerResponseExtensions.kt example. Determine where Kotlin extensions for this service belong and verify that the proposed await-based lookups return the expected user details, authorities, and roles.