How can we enable support for the spring security kotlin DSL?

As you can see from the Screenshot of the IDE (IntelliJ), the DSL is not available:

This is the full SecurityConfig.kt file:

package com.example.backend.core

import org.springframework.context.annotation.Bean
import org.springframework.security.config.annotation.web.reactive.EnableWebFluxSecurity
import org.springframework.security.config.web.server.ServerHttpSecurity
import org.springframework.security.web.server.SecurityWebFilterChain

@EnableWebFluxSecurity
class SecurityConfig {

  @Bean
  fun springSecurityFilterChain(http: ServerHttpSecurity): SecurityWebFilterChain? {
    return http {
      csrf { disable() }
      formLogin { disable() }
      httpBasic { disable() }
      // ...
    }
  }

}

This is our build.gradle.kts

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

val springBootVersion = "2.4.2"

plugins {
    id("org.springframework.boot") version "2.4.2"
    id("io.spring.dependency-management") version "1.0.11.RELEASE"
    kotlin("jvm") version "1.4.21"
    kotlin("plugin.spring") version "1.4.21"
}

group = "com.example"
version = "0.0.1-SNAPSHOT"
java.sourceCompatibility = JavaVersion.VERSION_11

configurations {
    compileOnly {
        extendsFrom(configurations.annotationProcessor.get())
    }
}

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-actuator")
    implementation("org.springframework.boot:spring-boot-starter-oauth2-resource-server")
    implementation("org.springframework.boot:spring-boot-starter-oauth2-client")
    implementation("org.springframework.boot:spring-boot-starter-security")
    implementation("org.springframework.boot:spring-boot-starter-webflux")
    implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
    implementation("io.projectreactor.kotlin:reactor-kotlin-extensions")
    implementation("org.flywaydb:flyway-core")
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
    developmentOnly("org.springframework.boot:spring-boot-devtools")
    runtimeOnly("io.micrometer:micrometer-registry-prometheus")
    runtimeOnly("org.postgresql:postgresql")
    annotationProcessor("org.springframework.boot:spring-boot-configuration-processor")
    testImplementation("org.springframework.boot:spring-boot-starter-test")
    testImplementation("io.projectreactor:reactor-test")
    testImplementation("org.springframework.security:spring-security-test")
}

tasks.withType<KotlinCompile> {
    kotlinOptions {
        freeCompilerArgs = listOf("-Xjsr305=strict")
        jvmTarget = "11"
    }
}

tasks.withType<Test> {
    useJUnitPlatform()
}

And this is the intellij version:

IntelliJ IDEA 2020.3 (Community Edition)
Build #IC-203.5981.155, built on November 30, 2020
Runtime version: 11.0.9+11-b1145.21 amd64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Linux 5.4.0-64-generic
GC: ParNew, ConcurrentMarkSweep
Memory: 1979M
Cores: 12
Registry: compiler.automake.allow.when.app.running=true
Non-Bundled Plugins: Key Promoter X, Dart, io.flutter, Lombook Plugin, org.jetbrains.kotlin
Current Desktop: X-Cinnamon

Do we miss some dependency? Does it require any specific intellij setup?