CORDA-939 Adding documentation changes requested from v3 release bran…

…ch PR (corda#2480)

* Adding documentation changes requested from v3 release branch PR

* Further doc changes as requested

docs/source/changelog.rst

@@ -170,6 +170,14 @@ UNRELEASED
 * Move to a message based control of peer to peer bridge formation to allow for future out of process bridging components.
   This removes the legacy Artemis bridges completely, so the ``useAMQPBridges`` configuration property has been removed.
 
+* A ``CordaInternal`` attribute has been added to identify properties that are not intended to form part of the
+  public api and as such are not intended for public use. This is alongside the existing ``DoNotImplement`` attribute for classes which
+  provide Corda functionality to user applications, but should not be implemented by consumers, and any classes which
+  are defined in ``.internal`` packages, which are also not for public use.
+
+* Marked ``stateMachine`` on ``FlowLogic`` as ``CordaInternal`` to make clear that is it not part of the public api and is
+  only for internal use
+
 .. _changelog_v1:
 
 Release 1.0

testing/node-driver/src/main/kotlin/net/corda/testing/node/NodeTestUtils.kt

@@ -6,11 +6,9 @@ import net.corda.core.concurrent.CordaFuture
 import net.corda.core.context.Actor
 import net.corda.core.context.AuthServiceId
 import net.corda.core.context.InvocationContext
-import net.corda.core.context.InvocationOrigin
 import net.corda.core.flows.FlowLogic
 import net.corda.core.identity.CordaX500Name
 import net.corda.core.identity.Party
-import net.corda.core.internal.FlowStateMachine
 import net.corda.core.node.ServiceHub
 import net.corda.core.serialization.internal.effectiveSerializationEnv
 import net.corda.core.transactions.TransactionBuilder
@@ -66,4 +64,8 @@ fun testContext(owningLegalIdentity: CordaX500Name = CordaX500Name("Test Company
  */
 fun StartedNodeServices.newContext() = testContext(myInfo.chooseIdentity().name)
 
+/**
+ * Starts an already constructed flow. Note that you must be on the server thread to call this method. [InvocationContext]
+ * has origin [Origin.RPC] and actor with id "Only For Testing".
+ */
 fun <T> StartedNodeServices.startFlow(logic: FlowLogic<T>): CordaFuture<T> = startFlow(logic, newContext()).getOrThrow().resultFuture