[BUG] SOAP request action doesn't get appended to Transaction Name

[Osch-1]

Intro

Hi! First - thank you for contributing this rep, it's very nice to be able to use apm even with old .net versions

APM Agent version

1.25.3

Environment

Operating system and version:
Windows 17763

.NET Framework/Core name and version (e.g. .NET 4.6.2, NET Core 3.1.100) :
Application Target Framework(s) (e.g. net462, netcoreapp3.1):
.NET Framework 4.7.2

Describe the bug

I have SOAP service, lets call it IntegrationService, it is hosted in IIS
The issue is that names of transactions that represent SOAP requests doesnt contain SOAP action, that is contained in body(in my case since it v1.2) or in SOAPAction header, so in result i have all my transactions "compressed" into one(attached screen)

To Reproduce

Steps to reproduce the behavior:
*I assume that u have elk set up and you are able to service to it

1. Setup simple SOAP service on .NetFramework 4.7.2, it must be hosted via IIS 10.0
   This service must contain at least one action, I'll call it GetProducts
2. Configure Elastic.Apm.Agent

3. Then make a request to GetProducts endpoint of your service
4. Go to Kibana -> APM
   You will see your service and your request represented as a transaction
   Name of this transaction will be "POST /Service.svc" without "GetProducts" part

Expected behavior

The name of the transaction must contain SOAP Action name, in this case GetProducts part
Full transaction name would be - "POST /Service.svc GetProducts"

Actual behavior

The name of the transaction doesn't contain "GetProducts" part

Bug cause

This behaviour is caused by this part of the code

apm-agent-dotnet/src/integrations/Elastic.Apm.AspNetFullFramework/ElasticApmModule.cs

Line 542 in d7b12fe

if (realTransaction == null || !realTransaction.HasCustomName)

This code won't work properly for common Apm Transaction class, since in case realTransaction is not null we will check if realTransaction.HasCustomName, but in case realTransaction is not null it will always be set to some value in code above(lines 455 - 533 of the same class - ElasticApmModule.cs)

Possible fix

If I'm it's actually a bug, I'd like to fix it, since I really want to use apm in my applications(actually multiple - about 10)
I see the next solution - remove if statement and always set this Action

I searched thour history of this repo and found another approach

It won't work, since setting Name property for instance of Transaction class will always set HasCustomName to true and your Code above are settings this property. We can work it out by providing NameInternal property in Transaction class

Hope you will reply soon, thank you in advance