Document DAP features that are not yet implemented in all IDEs about debug-adapter-protocol

[PavelSosin]

This issue is actually comprise 2 different issues:

• 1. For which scenario the message is relevant
• 2. In which IDE and DA the message is implemented
     There is no 100% suitable IDEs for every goal. This was also mentioned by Erich Gamma in his Cloud native IDE proposal. Every developer can choose most suitable for his/her goals front-end. IDE infrastructure provides UI backend (VSCode, Theia) and platform services (git, DevOps, Team development support, Doc generators, set of LSP servers and Debugging servers. Infrastructure can be local, cloud or hybrid.

The IDE purpose is to serve in certain scenario:

1. Local desktop application development
2. Consumer and businesses application development
3. Native cloud micro-services development
4. • (new) Cloud gaming development
5. To avoid dealing with very big matrix I propose to define 2 protocol layers:
   Core protocol applicable in all scenaria and Protocol extension used in certain scenario and implemented by certain IDEs
   Core protocol is mandatory for implementation by all IDE and DA
   Protocol extension can be implemented by certain IDE and DA. If certain IDE doesn't support certain message it doesn't harm its DAP protocol compatibility. Optional messages / message sequences should be communicated via Server and Client capabilities. Default values of capability shall be chosen according expected percentage of developers for which this feature is required

[PavelSosin]

SAP Web IDE doesn't support any low-level debugging features:
Register access
Memory read
Dissassembly
SAP WebIDE provides more fine-grained resolution for language context: language+projectType= contentType. The reason is that the same language can be used at more than one layer of application stack but with absolutely different built-in libraries: Typescript for SAPUI5 and typescript for Nodejs

[PavelSosin]

@weinand - Since in most cases IDE has debugger feature built on top of low-level debugging protocols or debugger server internally uses low-level debugging protocol I think it will be the correct to add reference map to corresponding low-level protocol call to justify request / notification usage.