Grid, fix toast for axios errors

[pierrejeambrun]

Error raised by axios (AxiosError) are not properly displayed in the toast. (Cf picture bellow).

AxiosError is a subclass of Error and therefore handled as standard Error, never reading from error.response.data but from error.message.

Added a check for Error deciding whether to read from error.message or error.response.data. (and removed the part that was never called after the Error check).

Updated the tests accordingly. Axios does not expose a way to construct AxiosError manually. (enhanceError, createError, AxiosError are not exposed because they are part of axios core). I constructed a custom object with the correct properties to be considered as an AxiosError from axios type guard (axios.isAxiosError). It is similar to what axios.enhanceError does. (If you have a better way to construct an AxiosError, I'd be glad to take it).

Before:

After: