Describe index part collation

[no1seman]

Product: Tarantool
Root document:
https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_space/create_index/
https://www.tarantool.io/en/doc/latest/book/box/indexes/

SME: @ no1seman, @ Totktonada

Details

Looks like the opportunity for index parts to have collation is only briefly described in the docs:

https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_space/create_index/

Definition of done

• Describe index collation options
• Describe index sort behavior when collation == nil
• Add an example for every collation type

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as any part of index may have collation - it must be accordingly described and also distinctly described index sort behavior when collation == nil.

Also it wiil be great if all available types of collation will be described too with examples.