Change BackEndDataProvider into an interface

[Legioth]

BackEndDataProvider is now an interface with methods for setting
sorting options based on SortOrder instances.

AbstractBackEndDataProvider stores sorting options, combines them with
the sorting provided in the query and invokes its own abstract fetch and
size methods.

CallbackDataProvider implements a BackEndDataProvider based on two
lambdas.

This is one of many steps towards #8245

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This change is 

[caalador]

Reviewed 11 of 11 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[denis-anisimov]

Reviewed 11 of 11 files at r1.
Review status: all files reviewed at latest revision, 3 unresolved discussions, all commit checks successful.

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server/src/main/java/com/vaadin/data/provider/BackEndDataProvider.java, line 61 at r1 (raw file):

     *            previously set sort orders
     */
    void setSortOrder(SortOrder<String> sortOrder);

It may have default impl.

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server/src/main/java/com/vaadin/data/provider/BackEndDataProvider.java, line 67 at r1 (raw file):

        return false;
    }
}

new line

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server/src/main/java/com/vaadin/data/provider/CallbackDataProvider.java, line 35 at r1 (raw file):

 *            data provider filter type
 */
public class CallbackDataProvider<T, F>

I would say CallbackDataProvider is a bad name here.
I have no idea from the name how "callback" is used here.

I'm not sure that I can come up with a better name
But may be DelegateDataProvider ?

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Comments from Reviewable

[Legioth]

Review status: 8 of 11 files reviewed at latest revision, 3 unresolved discussions.

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server/src/main/java/com/vaadin/data/provider/BackEndDataProvider.java, line 61 at r1 (raw file):

Previously, denis-anisimov (Denis) wrote…

It may have default impl.

Nice catch! Done.

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server/src/main/java/com/vaadin/data/provider/BackEndDataProvider.java, line 67 at r1 (raw file):

Previously, denis-anisimov (Denis) wrote…

new line

Done.

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server/src/main/java/com/vaadin/data/provider/CallbackDataProvider.java, line 35 at r1 (raw file):

Previously, denis-anisimov (Denis) wrote…

I would say CallbackDataProvider is a bad name here.
I have no idea from the name how "callback" is used here.

I'm not sure that I can come up with a better name
But may be DelegateDataProvider ?

To me, "delegate" is even less specific than what "callback" is.

Two related ideas would be LambdaDataProvider or FunctionDataProvider.

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Comments from Reviewable

[denis-anisimov]

Reviewed 2 of 3 files at r2.
Review status: 10 of 11 files reviewed at latest revision, 1 unresolved discussion.

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server/src/main/java/com/vaadin/data/provider/CallbackDataProvider.java, line 35 at r1 (raw file):

Previously, Legioth (Leif Åstrand) wrote…

To me, "delegate" is even less specific than what "callback" is.

Two related ideas would be LambdaDataProvider or FunctionDataProvider.

Definitely not Lambda .

Callback wouldn't be so bad in case there wasn't confusion about "consumes a callback" against "it is (or gives) a callback".
I would assume from the name that it is a callback.

I don't know.
Unblocked.

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Comments from Reviewable

[denis-anisimov]

Reviewed 1 of 3 files at r2.
Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable