test: Extract test for issue 450 from examples-grails-data-service

The fix for #450 did not really fit in `examples-grails-data-service`.

This commit adds a new example project, that shows the problem and that it now works (taken from https://github.com/grails-core-issues-forks/multitenantcomposite).

Author: matrei

examples/issue450/build.gradle

@@ -0,0 +1,36 @@
+plugins {
+    id 'com.bertramlabs.asset-pipeline' version '5.0.1'
+    id 'groovy'
+    id 'org.grails.grails-gsp'
+    id 'org.grails.grails-web'
+}
+
+version = rootProject.version
+group = 'multitenantcomposite'
+
+dependencies {
+
+    implementation project(':grails-plugin')
+    implementation 'org.grails:grails-core'
+    implementation 'org.grails:grails-plugin-rest'
+    implementation 'org.grails.plugins:gsp'
+
+    runtimeOnly 'com.bertramlabs.plugins:asset-pipeline-grails'
+    runtimeOnly 'com.h2database:h2'
+    runtimeOnly 'com.zaxxer:HikariCP'
+    runtimeOnly 'org.grails:grails-plugin-databinding'
+    runtimeOnly 'org.grails:grails-plugin-i18n'
+    runtimeOnly 'org.grails:grails-plugin-services'
+    runtimeOnly 'org.grails:grails-plugin-url-mappings'
+    runtimeOnly 'org.grails.plugins:fields'
+    runtimeOnly 'org.springframework.boot:spring-boot-autoconfigure'
+    runtimeOnly 'org.springframework.boot:spring-boot-starter-logging'
+    runtimeOnly 'org.springframework.boot:spring-boot-starter-tomcat'
+
+    integrationTestImplementation platform("io.micronaut.platform:micronaut-platform:$micronautPlatformVersion")
+    integrationTestImplementation 'io.micronaut:micronaut-http-client'
+    integrationTestImplementation 'org.grails:grails-testing-support'
+    integrationTestImplementation 'org.spockframework:spock-core'
+
+    integrationTestRuntimeOnly 'io.micronaut.serde:micronaut-serde-jackson'
+}