Replace Reactive awaitSingle() usages by the Mono variant

Closes gh-31127

spring-messaging/src/main/kotlin/org/springframework/messaging/rsocket/RSocketRequesterExtensions.kt

@@ -19,7 +19,7 @@ package org.springframework.messaging.rsocket
 import io.rsocket.transport.ClientTransport
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.reactive.asFlow
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.awaitSingleOrNull
 import org.reactivestreams.Publisher
 import org.springframework.core.ParameterizedTypeReference

spring-r2dbc/src/main/kotlin/org/springframework/r2dbc/core/UpdatedRowsFetchSpecExtensions.kt

@@ -16,7 +16,7 @@
 
 package org.springframework.r2dbc.core
 
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 
 /**
  * Coroutines variant of [UpdatedRowsFetchSpec.rowsUpdated].

spring-web/src/main/kotlin/org/springframework/web/server/ServerWebExchangeExtensions.kt

@@ -17,7 +17,7 @@
 package org.springframework.web.server
 
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.mono
 import org.springframework.http.codec.multipart.Part
 import org.springframework.util.MultiValueMap

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/client/ClientResponseExtensions.kt

@@ -18,7 +18,7 @@ package org.springframework.web.reactive.function.client
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.reactor.awaitSingleOrNull
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactive.asFlow
 import org.springframework.core.ParameterizedTypeReference
 import org.springframework.http.ResponseEntity

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/client/WebClientExtensions.kt

@@ -19,7 +19,7 @@ package org.springframework.web.reactive.function.client
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.reactive.asFlow
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.awaitSingleOrNull
 import kotlinx.coroutines.reactor.asFlux
 import kotlinx.coroutines.reactor.mono

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/CoRouterFunctionDsl.kt

@@ -17,7 +17,7 @@
 package org.springframework.web.reactive.function.server
 
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.mono
 import org.springframework.core.io.Resource
 import org.springframework.http.HttpMethod

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/RenderingResponseExtensions.kt

@@ -16,7 +16,7 @@
 
 package org.springframework.web.reactive.function.server
 
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 
 /**
  * Coroutines variant of [RenderingResponse.Builder.build].

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerRequestExtensions.kt

@@ -18,7 +18,7 @@ package org.springframework.web.reactive.function.server
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.reactor.awaitSingleOrNull
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactive.asFlow
 import org.springframework.core.ParameterizedTypeReference
 import org.springframework.http.MediaType

spring-webflux/src/main/kotlin/org/springframework/web/reactive/function/server/ServerResponseExtensions.kt

@@ -17,7 +17,7 @@
 package org.springframework.web.reactive.function.server
 
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import org.reactivestreams.Publisher
 import org.springframework.core.ParameterizedTypeReference
 import org.springframework.http.MediaType

spring-webflux/src/main/kotlin/org/springframework/web/reactive/server/ServerWebExchangeExtensions.kt

@@ -17,7 +17,7 @@
 package org.springframework.web.reactive.server
 
 import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.reactive.awaitSingle
+import kotlinx.coroutines.reactor.awaitSingle
 import kotlinx.coroutines.reactor.mono
 import org.springframework.http.codec.multipart.Part
 import org.springframework.util.MultiValueMap