make dash examples work w/ python 3

Dependency tree

Fix race conditions

Copy metadata into py pkg before publishing

Copy metadata into py pkg before publishing

* ∙ - remove contextvar from flask and quart only FastApi now relies on that
∙ - backend __init__ now holds the global request adapter and backend which get set on app initialisation
∙ request adapter and server can now be call from everywhere after the app initialised
∙ - added normal top level imports because the modules get matching loaded - but bad Import Error message when quart or equivilent are not installed
∙ - added _ as prefix to backends to avoid importing errors with their underlying
∙ - Can now move to remove unnecessary passing of the server object
∙

* Moved get_server_type to backends

* ∙ moved async validation to validation
∙ replaced request.get_path with request.path
∙

* Moved custom backend check to _validation.py

* Removed server injection of server methods - they use self.server now

* removed use_async from dispatch server methods and use dash_app._use_async
removed remaining set request process from flask

* adding custom error handling per backend, tests and adjustments to the flow. Made endpoints for downloading the reqs

* adjusments for formatting

* adjustment to retest backend

* Added Dash app as type to servers

* adding missing reqs association

* Addedd basic typing to servers

* fixing minor linting issues

* Fixed weird AI shit

* Cleanup before heavy pull

* Merged latest changes

* f rebase

* f rebase

* Added Dash app as type to servers

* Addedd basic typing to servers

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Co-authored-by: Christian Giessel <cgiessel@tesla.com>
Co-authored-by: BSd3v <82055130+BSd3v@users.noreply.github.com>