Base Schema builder is returned in some builder methods.

[Amartel1986]

When trying to build a concrete schema using it's builder I met a strange situation when methods calling order matters because of their return types.

For example this code is valid:

        StringSchema stringValue = StringSchema.builder()
            .maxLength(10)
            .title("String value")
            .build();

while this is not:

        StringSchema stringValue = StringSchema.builder()
            .title("String value")
            .maxLength(10)
            .build();

This feels like a bug to me.

One of the possible solutions is to use a concrete builder as a generic parameter:

    public abstract class Schema {
        public abstract static class Builder<S extends Schema, B extends Builder> {
            public B title(String title) {
                this.title = title;
                //noinspection unchecked
                return (B) this;
            }
        }
    }

    public class StringSchema extends Schema {
        public static class Builder extends Schema.Builder<StringSchema, Builder> {

        }
    }

[JoshMcCullough]

I agree. Any time you use a builder method in the superclass Schema.Builder<S extends Schema>, you are returned a Builder<S> rather than the original builder (e.g. ObjectSchemaBuilder). So you no longer have fluent access to the methods off of the actual builder.

[JoshMcCullough]

Fixed by #390 -- breaking change though.