Concatenate schemas with fields or other schemas

[georgolden]

@lundibundi please edit

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User { name: 'string' } => User { name: 'string', age: 'number', fullName: 'string' }

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[georgolden]

@lundibundi I think it is better to create another schema rather then mixin into existing one. What do you think?

And how to deal with conflicts if 2 schemas have same field with different type? Error throw?

[georgolden]

1. create a fork of this repo
2. use npm ci to install deps
3. create a branch named feature/concat-schemas
4. create a test for a this feature

Requirements.

• This must be a method Schema.concat(...schemas ) returns new Schema that contains fields from 2 schemas.
• If schemas are conflicting, e.g. they have similar fields with different typings, error must be thrown
• metadata of resulting schema must contatin metadata from both schemas
• if schemas have different KIND - throw error

[dmitryt]

I'd like to take this one