Discuss new Framework API structure

This issue is intended to be a discussion point for the new PowerShell Editor Services API model. The idea here is that Editor Services will now become a framework for adding new capabilities to editors that use it. The overall goal being that most non-core functionality will be enabled through modules that plug into the Editor Services APIs. PSScriptAnalyzer, Plaster, and other modules will add functionality directly through these APIs rather than PSES having to know about them and manage their integration.

Interfaces

All of these interface and method are subject to change as we develop the ideas further.

• IWorkspace - Provides access to the files in the current workspace and events for when files are opened, closed, changed, or saved
• ILogger - Writing logs to the Editor Services log. Important for module integrations to log their activities
• IFileMarkers - Adding markers to files, like those from PSScriptAnalyzer. Also providing quick fixes for these markers
• IMessageHandlers - Registering message handlers for both Language Server Protocol messages and custom message types
• ICodeLensProvider - Providing "code lenses" at arbitrary locations in the script which provide information and launch actions at that point
• IEditorCommands - Registering extension commands in the editor which show up in the command palette
• ICompletionsProvider - Providing custom completions (and snippets) in addition to the built-in completions and snippets
• IFileSymbols - Gathering information about symbols in a particular file
• IWorkspaceSymbols - Gathering information about symbols across the workspace
• IWindowMessages (?) - Showing messages in the editor window (ShowErrorMessage, etc)
• IWindowPrompts - Showing prompts natively in the editor's UI, mirrors the prompting functionality in the PSHostUserInterface API
• IDebuggerCommmands - Provides commands for the debugger, like breaking, stepping, continuing, etc
• IDebuggerEvents - Exposes events for the debugger, primarily around stopping and resuming
• IRunspaceEvents - Exposes events for when the active runspace changes, like when a remote session is established
• ICommandExecution - Commands for executing commands against the current runspace. Also exposes events that give state change information for command execution

TODO: Add more interfaces here

Please feel free to leave comments below to discuss APIs you'd like to see!

The issue names no files, tests, or entry points. Start by reviewing the current Editor Services API structure and the listed interface proposals; this discussion is not complete until a concrete API scope and implementation target have been agreed.