set automatically coerce_shape for xarray_image

I have a local directory with GeoTIFF files with different shapes. I've explored the `coerce_shape` parameter to define manually a certain shape. I'm wondered if there's a workaround to coerce all images according to the largest shape in the directory instead of defining it manually. The following lines show how I define the catalog:

```
[...]
sources:
test1:
driver: xarray_image
args:
urlpath: '{{ CATALOG_DIR }}/data/*.tif'
coerce_shape: [400,400]
[...]
```