Restore Format and CheckFormat for saml2 Projects

- Update the way that the saml2 projects were dependent
on identity-provider resource files.
- Use TestContainers to simplify runtime dependencies
- Update compose.yml to use Docker-standard interpolation

Closes gh-335

servlet/spring-boot/java/saml2/refreshable-metadata/build.gradle

@@ -13,9 +13,6 @@ repositories {
 	maven { url "https://build.shibboleth.net/nexus/content/repositories/releases/" }
 }
 
-sourceSets.main.java.srcDirs += "$projectDir/../identity-provider/src/main/java"
-sourceSets.main.resources.srcDirs += "$projectDir/../identity-provider/src/main/resources"
-
 dependencies {
 	constraints {
 		implementation "org.opensaml:opensaml-saml-api:5.1.2"
@@ -27,6 +24,9 @@ dependencies {
 	implementation 'org.springframework.security:spring-security-saml2-service-provider'
 	implementation 'org.thymeleaf.extras:thymeleaf-extras-springsecurity6'
 
+	runtimeOnly files("$projectDir/../identity-provider/build/resources/main")
+
+	testImplementation project(':servlet:spring-boot:java:saml2:identity-provider')
 	testImplementation 'org.htmlunit:htmlunit'
 	testImplementation 'org.springframework.boot:spring-boot-starter-test'
 	testImplementation 'org.springframework.security:spring-security-test'