Disk Format
* Removed file `__coords.tdb` that stored the zipped coordinates in sparse fragments
* Now storing the coordinate tiles on each dimension in separate files
* Changed fragment name format from `__t1_t2_uuid` to `__t1_t2_uuid_<format_version>`. That was necessary for backwards compatibility
Breaking C API changes
* Changed `domain` input of `tiledb_dimension_get_domain` to `const void**` (from `void**`).
* Changed `tile_extent` input of `tiledb_dimension_get_tile_extent` to `const void**` (from `void**`).
* Anonymous attribute and dimensions (i.e., empty strings for attribute/dimension names) is no longer supported. This is because now the user can set separate dimension buffers to the query and, therefore, supporting anonymous attributes and dimensions creates ambiguity in the current API.
Breaking behavior
* Now the TileDB consolidation process does not clean up the fragments or array metadata it consolidates. This is (i) to avoid exclusively locking at any point during consolidation, and (ii) to enable fine-grained time traveling even in the presence of consolidated fragments or array metadata. Instead, we added a special vacuuming API which explicitly cleans up consolidated fragments or array metadata (with appropriate configuration parameters). The vacuuming functions briefly exclusively lock the array.
New features
* Added string dimension support (currently only `TILEDB_STRING_ASCII`).
* The user can now set separate coordinate buffers to the query. Also any subset of the dimensions is supported.
* The user can set separate filter lists per dimension, as well as the number of values per coordinate.
Improvements
* Added support for AWS Security Token Service session tokens via configuration option `vfs.s3.session_token`. [1472](https://github.com/TileDB-Inc/TileDB/pull/1472)
* Added support for indicating zero-value metadata by returning `value_num` == 1 from the `_get_metadatata` and `Array::get_metadata` APIs [1438](https://github.com/TileDB-Inc/TileDB/pull/1438) (this is a non-breaking change, as the documented return of `value == nullptr` to indicate missing keys does not change)`
* User can set coordinate buffers separately for write queries.
* Added option to enable duplicate coordinates for sparse arrays [1504](https://github.com/TileDB-Inc/TileDB/pull/1504)
* Added support for writing at a timestamp by allowing opening an array at a timestamp (previously disabled).
* Added special files with the same name as a fragment directory and an added suffix ".ok", to indicate a committed fragment. This improved the performance of opening an array on object stores significantly, as it avoids an extra REST request per fragment.
* Added functionality to consolidation, which allows consolidating the fragment metadata footers in a single file by toggling a new config parameter. This leads to a huge performance boost when opening an array, as it avoids fetching a separate footer per fragment from storage.
* Various reader parallelizations that boosted read performance significantly.
* Configuration parameters can now be read from environmental variables. `vfs.s3.session_token` -> `TILEDB_VFS_S3_SESSION_TOKEN`. The prefix of `TILEDB_` is configurable via `config.env_var_prefix`. [1600](https://github.com/TileDB-Inc/TileDB/pull/1600)
Deprecations
* The TileDB tiledb_array_consolidate_metadata and tiledb_array_consolidate_metadata_with_key C-API routines have been deprecated and will be [removed entirely](https://github.com/TileDB-Inc/TileDB/issues/1591) in a future release. The tiledb_array_consolidate and tiledb_array_consolidate_with_key routines achieve the same behavior when the "sm.consolidation.mode" parameter of the configuration argument is equivalent to "array_meta".
* The TileDB Array::consolidate_metadata CPP-API routine has been deprecated and will be [removed entirely](https://github.com/TileDB-Inc/TileDB/issues/1591) in a future release. The Array::consolidate routine achieves the same behavior when the "sm.consolidation.mode" parameter of the configuration argument is equivalent to "array_meta".
Bug fixes
* Fixed bug in dense consolidation when the array domain is not divisible by the tile extents.
API additions
* Added C API function `tiledb_array_has_metadata_key` and C++ API function `Array::has_metadata_key` [1439](https://github.com/TileDB-Inc/TileDB/pull/1439)
* Added C API functions `tiledb_array_schema_{set,get}_allows_dups` and C++ API functions `Array::set_allows_dups` and `Array::allows_dups`
* Added C API functions `tiledb_dimension_{set,get}_filter_list` and `tiledb_dimension_{set,get}_cell_val_num`
* Added C API functions `tiledb_array_get_non_empty_domain_from_{index,name}`
* Added C API function `tiledb_array_vacuum`
* Added C API functions `tiledb_array_get_non_empty_domain_var_size_from_{index,name}`
* Added C API functions `tiledb_array_get_non_empty_domain_var_from_{index,name}`
* Added C API function `tiledb_array_add_range_var`
* Added C API function `tiledb_array_get_range_var_size`
* Added C API function `tiledb_array_get_range_var`
* Added C++ API functions `Dimension::set_cell_val_num` and `Dimension::cell_val_num`.
* Added C++ API functions `Dimension::set_filter_list` and `Dimension::filter_list`.
* Added C++ API functions `Array::non_empty_domain(unsigned idx)` and `Array::non_empty_domain(const std::string& name)`.
* Added C++ API functions `Domain::dimension(unsigned idx)` and `Domain::dimension(const std::string& name)`.
* Added C++ API function `Array::load_schema(ctx, uri)` and `Array::load_schema(ctx, uri, key_type, key, key_len)`.
* Added C++ API function `Array::vacuum`.
* Added C++ API functions `Array::non_empty_domain_var` (from index and name).
* Added C++ API function `add_range` with string inputs.
* Added C++ API function `range` with string outputs.
* Added C++ API functions `Array` and `Context` constructors which take a c_api object to wrap. [1623](https://github.com/TileDB-Inc/TileDB/pull/1623)
API removals