request: language support for inverse relations

[vroldanbet]

The ask

SpiceDB language could have native support to denote the inverse of a relationship

Example:

definition repository {
  relation owner: User
}

definition user {
  inverse relation repositories: repository#owner
}

The goal

• At very large scale, writing 2 tuples instead of one would incur additional COGS for the underlying database system
• It removes the burden from the client-side to maintain those two relationships. With large and complex schemas, it could be difficult to keep track of all the relationships that need to be written when a new entity is persisted in the application side. As complexity increases, there could be higher chances to have inconsistent data persisted in SpiceDB

[jhalleeupgrade]

Adding a +1 on this issue. We found ourselves needing to add inverse relationships for most of our use-cases.