Feature: Constant values
@const
Scenario: const
Given a YAML schema:
```
type: object
properties:
country:
const: United States of America
```
Then it should accept:
```
country: United States of America
```
But it should NOT accept:
```
country: Canada
```
Scenario: const with array value
Given a YAML schema:
```
type: object
properties:
coordinates:
const: [1, 2]
```
Then it should accept:
```
coordinates: [1, 2]
```
But it should NOT accept:
```
coordinates: [1, 3]
```
And it should NOT accept:
```
coordinates: [1, 2, 3]
```
Scenario: const with object value
Given a YAML schema:
```
type: object
properties:
config:
const:
env: production
debug: false
```
Then it should accept:
```
config:
env: production
debug: false
```
But it should NOT accept:
```
config:
env: development
debug: false
```
And it should NOT accept:
```
config:
env: production
```