This commit makes possible to pass an optional `X-Garg-Error-Scheme`
header in a client request to enable the new error format.

It was only for test for now.

Added more tests for more subtle cases.

Also, some fixes to NodeStory (it inserts ngrams when saving node
story, when they don't exist).

This commit introduces a new DB function called `isSharedWith`
that can be used to check for team/public/private nodes and their
shared resources.

(no default getCurrentTime anymore)

This is a first stepping stone in avoiding bugs by having `UserId` and
`ContextId` being proper types, and not synonyms.

We also refactor things to have `AuthenticatedUser` carry the `UserId`.

Basically, Gargantext.Prelude exports all of Protolude now.

- DBCmd instead of Cmd
- remove FlowCmdM in favor of HasNodeStory

This commit partially undo the access policy checks for the
GraphQL endpoints, until we find a better story to correlate
the `user_id` we sometimes receive with the info from the
`AuthenticatedUser`.

This commit makes the `GET /api/v1.0/version` test more lax, and less
prone to break on version bumps.

It can be used to "bolt-on" policy checking into Servant API routes.