Plugin [id: 'org.jetbrains.kotlin.plugin.spring'] not found error when defining plugin in .gradle.kts files under buildSrc directory - kotlin

Question

I am trying to create plugins for a multi-module Kotlin application such as build configurations can be more easily maintained shared among several modules (core, model, lib, app) using Gradle 6.8.1.
At the root project directory, gradle init is executed and the following options are inputted.
option
selection
type
application
language
Kotlin
multiple subprojects
yes
build script DSL
Kotlin
The following .gradle.kts files are generated under buildSrc/src/main/kotlin directory.
my.package.kotlin-applications.gradle.kts
my.package.kotlin-common-conventions.gradle.kts
my.package.kotlin-library-conventions.gradle.kts
As I will be using Spring Boot features, I am trying to add several plugins in my.package.kotlin-library-conventions.gradle.kts which will be used by lib and app modules.
plugins {
id("my.package.kotlin-common-conventions")
// new plugins
kotlin("plugin.spring")
id("org.springframework.boot")
id("io.spring.dependency-management")
`java-library`
}
When I execute gradle build, the following error is returned.
Plugin [id: 'org.jetbrains.kotlin.plugin.spring'] was not found in any of the following sources:
- Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
- Plugin Repositories (plugin dependency must include a version number for this source)
I tried to edit the contents in below files but still cannot resolve the above error.
settings.gradle.kts
pluginManagement {
repositories {
jcenter()
gradlePluginPortal()
maven { url = uri("https://repo.spring.io/milestone") }
maven { url = uri("https://repo.spring.io/snapshot") }
}
plugins {
kotlin("jvm") version "1.4.21-2"
kotlin("plugin.spring") version "1.4.21-2"
id("org.springframework.boot") version "2.5.0-SNAPSHOT"
id("io.spring.dependency-management") version "1.0.11.RELEASE"
}
}
buildSrc/build.gradle.kts
plugins {
`kotlin-dsl`
kotlin("plugin.spring")
id("org.springframework.boot")
id("io.spring.dependency-management")
}
repositories {
gradlePluginPortal()
jcenter()
maven { url = uri("https://repo.spring.io/milestone") }
maven { url = uri("https://repo.spring.io/snapshot") }
}
dependencies {
implementation("org.jetbrains.kotlin:kotlin-gradle-plugin")
}