Ensure URI can be obtained from a wider variety of containers (#25)

* Use first available port instead of hardcoding `80`

* Use `SingleContainer` instead of `GenericContainer` since it is higher

* Add needed suppression

modules/http4s-munit-testcontainers/src/main/scala/munit/LowPrecedenceContainer2Uri.scala

@@ -16,12 +16,14 @@
 
 package munit
 
-import com.dimafeng.testcontainers.GenericContainer
+import com.dimafeng.testcontainers.SingleContainer
 import org.http4s.Uri
+import org.testcontainers.containers.GenericContainer
 
+@SuppressWarnings(Array("scalafix:Disable.head"))
 trait LowPrecedenceContainer2Uri {
 
-  implicit def GenericContainer2Uri[A <: GenericContainer]: A => Uri = container =>
-    Uri.unsafeFromString(s"http://localhost:${container.mappedPort(80)}")
+  implicit def GenericContainer2Uri[A <: SingleContainer[GenericContainer[_]]]: A => Uri = container =>
+    Uri.unsafeFromString(s"http://localhost:${container.mappedPort(container.exposedPorts.head)}")
 
 }