Doc: use custom sharding key to calculate bucket id

Describe functionality and current limitations (#212, #213 and #219)
with custom sharding key in CHANGELOG and README.

Closes #166

Author: ligurio

CHANGELOG.md

@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * `crud.len()` function to calculate the number of tuples
   in the space for memtx engine and calculate the maximum
   approximate number of tuples in the space for vinyl engine.
+<<<<<<< HEAD
 * Testing: added integration with service coveralls.io (PR #195).
 * Testing: added integration with luacov that allows to generate report with
   code coverage statistics (PR #195).
@@ -44,6 +45,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Ignoring of an error in `crud.pairs()` (#144).
 * Damaging of opts table by CRUD methods (#192).
 * Ignoring of `bucket_id` option in `crud.select()`/`crud.pairs()` (#220).
+=======
+* CRUD operations calculates bucket id automatically using sharding
+  key specified with DDL schema or in `_ddl_sharding_key` space.
+  NOTE: CRUD methods delete(), get() and update() requires that sharding key
+  must be a part of primary key.
+>>>>>>> 777933f... Doc: use custom sharding key to calculate bucket id
 
 ## [0.8.0] - 02-07-21
 

README.md

@@ -162,7 +162,8 @@ local object, err = crud.get(space_name, key, opts)
 where:
 
 * `space_name` (`string`) - name of the space
-* `key` (`any`) - primary key value
+* `key` (`any`) - primary key value in version < 0.8.0 and sharding key when
+  DDL sharding key is used in version >= 0.8.0. See section 'Sharding key' above.
 * `opts`:
   * `fields` (`?table`) - field names for getting only a subset of fields
   * `bucket_id` (`?number|cdata`) - bucket ID
@@ -199,7 +200,8 @@ local object, err = crud.update(space_name, key, operations, opts)
 where:
 
 * `space_name` (`string`) - name of the space
-* `key` (`any`) - primary key value
+* `key` (`any`) - primary key value in version < 0.8.0 and sharding key when
+  DDL sharding key is used in version >= 0.8.0. See section 'Sharding key' above.
 * `operations` (`table`) - update [operations](https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_space/#box-space-update)
 * `opts`:
   * `timeout` (`?number`) - `vshard.call` timeout (in seconds)
@@ -232,7 +234,8 @@ local object, err = crud.delete(space_name, key, opts)
 where:
 
 * `space_name` (`string`) - name of the space
-* `key` (`any`) - primary key value
+* `key` (`any`) - primary key value in version < 0.8.0 and sharding key when
+  DDL sharding key is used in version >= 0.8.0. See section 'Sharding key' above.
 * `opts`:
   * `timeout` (`?number`) - `vshard.call` timeout (in seconds)
   * `bucket_id` (`?number|cdata`) - bucket ID