Query Node: Add membership relation to Curator Entity

Currently, the QN schema for the `Curator` entity is as follows:

```.graphql
type Curator @entity {
"Runtime identifier"
id: ID!

"Type needs to have at least one non-relation entity. This value is not used."
dummy: Int

"Curator belonging to this group with their permissions."
curatorGroups: [CuratorAgentPermissions!]! @derivedFrom(field: "curator")
}
```
## Proposal

Add the `member` field to the curator entity linking it to the corresponding membership.
```.gql
"Member corresponding to this curator"
member: Membership!
```
That will be useful for querying member's `infrastructureAccessKeys` through curator/s when authenticating specific personae/role for fetching assets from Argus