Error management

[Kuenssi]

Currently there is no feedback for the user if he did something wrong.

Should use the toasts with error messages from the backend.

Maybe some kind of linter for the codemirror would be nice. (Look into json-schema check a string, with typescript angular)

[Kuenssi]

Linter in frontend using the json schema already created.

Beautiful tip from Seb: https://github.com/ajv-validator/ajv

[Kuenssi]

Left for the bachelor thesis:

• [x] Parse the error to an easy understandable message and show it in toast

[Kuenssi]

done