CelVariableResolver

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
```
@FunctionalInterface
public interface CelVariableResolver
```
Functional interface that exposes a method to find a CEL variable value by name.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.util.Optional<java.lang.Object>`	`find(java.lang.String name)`	Find a variable value, if present, by `name`.
`static CelVariableResolver`	`hierarchicalVariableResolver(CelVariableResolver primary, CelVariableResolver secondary)`	Chain two variable resolvers together, using the `primary` as the initial variable source to consider, and the `secondary` as a backup.

- Method Detail
  - find
```
java.util.Optional<java.lang.Object> find(java.lang.String name)
```
    Find a variable value, if present, by name.
    Variable String names may be simple, e.g. status or qualified pkg.qual.status. CEL resolves identifiers within an expression container using protobuf namespace resolution rules.
    For example, given an expression container name a.b.c.M.N and a variable name R.s, CEL evaluators will try resolve names in the following order:
    
    a.b.c.M.N.R.s
    a.b.c.M.R.s
    a.b.c.R.s
    a.b.R.s
    a.R.s
    R.s
  - hierarchicalVariableResolver
```
static CelVariableResolver hierarchicalVariableResolver(CelVariableResolver primary,
                                                        CelVariableResolver secondary)
```
    Chain two variable resolvers together, using the primary as the initial variable source to consider, and the secondary as a backup.
    When a variable appears in both resolvers, then the primary variable value will shadow the value in the secondary.