Ensure nodata=nan tags are written to floating point COGs. (#355)

* Ensure nodata=nan tags are written to floating point COGs.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Typo.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Fix logic and cleanup.

* Use numpy.nan for consistency with core.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

eodatasets3/images.py

@@ -710,6 +710,10 @@ def write_from_ndarray(
             "driver": "GTiff",
             "predictor": self.PREDICTOR_DEFAULTS[dtype],
         }
+        # Ensure 'nan' is always tagged as nodata for floating point types
+        if nodata is None and numpy.issubdtype(array.dtype, numpy.floating):
+            nodata = numpy.nan
+
         if nodata is not None:
             rio_args["nodata"] = nodata