Migrate to provider API adding configuration cache compatibility

Using the provider API defers configuration work until it is needed, reducing configuration time.
Furthermore, it is required for making the build configuration cache compatible.

build.gradle.kts

@@ -1,7 +1,8 @@
 import org.jetbrains.changelog.Changelog
 import org.jetbrains.changelog.markdownToHTML
 
-fun properties(key: String) = project.findProperty(key).toString()
+fun properties(key: String) = providers.gradleProperty(key)
+fun environment(key: String) = providers.environmentVariable(key)
 
 plugins {
     // Java support
@@ -38,21 +39,21 @@ intellij {
     type.set(properties("platformType"))
 
     // Plugin Dependencies. Uses `platformPlugins` property from the gradle.properties file.
-    plugins.set(properties("platformPlugins").split(',').map(String::trim).filter(String::isNotEmpty))
+    plugins.set(properties("platformPlugins").map { it.split(',').map(String::trim).filter(String::isNotEmpty) })
 }
 
 // Configure Gradle Changelog Plugin - read more: https://github.com/JetBrains/gradle-changelog-plugin
 changelog {
-    groups.set(emptyList())
+    groups.empty()
     repositoryUrl.set(properties("pluginRepositoryUrl"))
 }
 
 // Configure Gradle Qodana Plugin - read more: https://github.com/JetBrains/gradle-qodana-plugin
 qodana {
-    cachePath.set(file(".qodana").canonicalPath)
-    reportPath.set(file("build/reports/inspections").canonicalPath)
+    cachePath.set(provider { file(".qodana").canonicalPath })
+    reportPath.set(provider { file("build/reports/inspections").canonicalPath })
     saveReport.set(true)
-    showReport.set(System.getenv("QODANA_SHOW_REPORT")?.toBoolean() ?: false)
+    showReport.set(environment("QODANA_SHOW_REPORT").map {  it.toBoolean() } .getOrElse(false))
 }
 
 // Configure Gradle Kover Plugin - read more: https://github.com/Kotlin/kotlinx-kover#configuration
@@ -62,7 +63,7 @@ kover.xmlReport {
 
 tasks {
     wrapper {
-        gradleVersion = properties("gradleVersion")
+        gradleVersion = properties("gradleVersion").get()
     }
 
     patchPluginXml {
@@ -71,23 +72,24 @@ tasks {
         untilBuild.set(properties("pluginUntilBuild"))
 
         // Extract the <!-- Plugin description --> section from README.md and provide for the plugin's manifest
-        pluginDescription.set(
-            file("README.md").readText().lines().run {
-                val start = "<!-- Plugin description -->"
-                val end = "<!-- Plugin description end -->"
-
-                if (!containsAll(listOf(start, end))) {
-                    throw GradleException("Plugin description section not found in README.md:\n$start ... $end")
-                }
-                subList(indexOf(start) + 1, indexOf(end))
-            }.joinToString("\n").let { markdownToHTML(it) }
+        pluginDescription.set(provider {
+                file("README.md").readText().lines().run {
+                    val start = "<!-- Plugin description -->"
+                    val end = "<!-- Plugin description end -->"
+
+                    if (!containsAll(listOf(start, end))) {
+                        throw GradleException("Plugin description section not found in README.md:\n$start ... $end")
+                    }
+                    subList(indexOf(start) + 1, indexOf(end))
+                }.joinToString("\n").let { markdownToHTML(it) }
+            }
         )
 
         // Get the latest available change notes from the changelog file
         changeNotes.set(provider {
             with(changelog) {
                 renderItem(
-                    getOrNull(properties("pluginVersion"))
+                    getOrNull(properties("pluginVersion").get())
                         ?: runCatching { getLatest() }.getOrElse { getUnreleased() },
                     Changelog.OutputType.HTML,
                 )
@@ -105,17 +107,17 @@ tasks {
     }
 
     signPlugin {
-        certificateChain.set(System.getenv("CERTIFICATE_CHAIN"))
-        privateKey.set(System.getenv("PRIVATE_KEY"))
-        password.set(System.getenv("PRIVATE_KEY_PASSWORD"))
+        certificateChain.set(environment("CERTIFICATE_CHAIN"))
+        privateKey.set(environment("PRIVATE_KEY"))
+        password.set(environment("PRIVATE_KEY_PASSWORD"))
     }
 
     publishPlugin {
         dependsOn("patchChangelog")
-        token.set(System.getenv("PUBLISH_TOKEN"))
+        token.set(environment("PUBLISH_TOKEN"))
         // The pluginVersion is based on the SemVer (https://semver.org) and supports pre-release labels, like 2.1.7-alpha.3
         // Specify pre-release label to publish the plugin in a custom Release Channel automatically. Read more:
         // https://plugins.jetbrains.com/docs/intellij/deployment.html#specifying-a-release-channel
-        channels.set(listOf(properties("pluginVersion").split('-').getOrElse(1) { "default" }.split('.').first()))
+        channels.set(properties("pluginVersion").map { listOf(it.split('-').getOrElse(1) { "default" }.split('.').first()) })
     }
 }