Create endpoint to get store type

[t92549]

Describe the new feature you'd like
An endpoint that would tell you what type of store you are querying.

Why do you want this feature?
Currently it is not possible to know if the graph you are querying is backed by a FederatedStore, an AccumuloStore, a ProxyStore or a MapStore. You can still ask what operations are available, but sometimes it is useful to know the store type.

Additional context
The entire store properties cannot be returned as they can contain information that should not be seen by users.

[GCHQDeveloper314]

What if we want to know what type of graph is the final backing graph? For example in the setup below this would return ProxyStore but I'm not sure how useful that is.

graph LR;
    User-->NearProxyStore;
    NearProxyStore-->FederatedStore;
    FederatedStore-->FarProxyStore;
    FarProxyStore-->AccumuloStore;

Loading

I think if we wanted to know the kind of remote store, then a new Operation would be required. This could be a follow up issue, not something to be done under this issue.

[GCHQDeveloper314]

As discussed in the related Gaffer version endpoint issue, this issue is just to create an endpoint which returns the type of Gaffer Store used in the endpoint itself. This will not allow for determining the type of store at the end of any chain of stores.

An operation would allow this, but that's not in scope of this ticket. As covered in the related ticket, if the local Gaffer instance is a ProxyStore it will not be possible to determine its store type using an operation, as this will always be passed through the proxy store and forwarded on. An endpoint will therefore be useful, and will only partially overlap with the capabilities of an operation.