Earthmover

<details>
<summary>Released 2023-05-02</summary>

* bugfix: fix continued issues with environment variable expansion under Windows by changing from `os.path.expandvars()` to native Python `String.Template` implementation
* bugfix: change how earthmover loads `config.macros` from YAML to prevent issues with multi-line macros definitions

</details>

<details>
<summary>Released 2023-03-27</summary>

* bugfix: a single quote in the config YAML could prevent environment variable expansion from working since `os.path.expandvars()` [does not expand variables within single quotes](https://hg.python.org/cpython/file/v2.7.3/Lib/ntpath.py#l330) in Python under Windows

</details>

<details>
<summary>Released 2023-03-23</summary>

* feature: added parse-time Jinja templating to YAML configuration

> :warning: **Potentially breaking change:** if your config YAML contains `add_columns` or `modify_columns` operations *with Jinja expressions*, these will now be parsed at YAML load time. To preserve the Jinja for runtime parsing, wrap the expressions with `{%raw%}...{%endraw%}`. See [YAML parsing](./README.mdyaml-parsing) for further information.

* feature: removed dependency on matplotlib, which is only required if your YAML specified `config.show_graph: True`... now if you try to `show_graph` without matplotlib installed, you'll get an error prompting you to install matplotlib

</details>

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<details>
<summary>Released 2023-02-23</summary>

* feature: added `str_min()` and `str_max()` functions for `group by` operation
</details>

<details>
<summary>Released 2023-02-17</summary>

* feature: pass `__row_data__` dict into Jinja templates for easier dynamic column referencing
* bugfix: parameter / env var interpolation into YAML keys, not just values
* refactor error handling key assertion methods
* refactor YAML loader line number context handling
</details>

<details>
<summary>Released 2022-12-16</summary>

* trim nodes not connected to a destination from DAG
* ensure all source datatypes return a Dask dataframe
* update [optional source functionality](optional-sources) to require `columns` list, and pass an empty dataframe through the DAG
</details>