id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1331985070,I_kwDOAMm_X85PZHqu,6891,Passing extra keyword arguments to `curvefit` throws an exception.,44142765,open,0,,,13,2022-08-08T14:47:56Z,2023-03-26T19:40:43Z,,NONE,,,,"### What happened?

Just like the title says, passing an extra keyword argument corresponding to scipy's `curve_fit` throws an exception. The [documentation](https://docs.xarray.dev/en/stable/generated/xarray.DataArray.curvefit.html) has a parameter section that says:
```
*kwargs (optional) – Additional keyword arguments to passed to scipy curve_fit
```

So if one specifies a `method=""trf""` keyword argument to the `.curvefit` method, you get an error: `TypeError: curvefit() got an unexpected keyword argument 'method'`

The only way it works as expected is if I pass the keyword arguments as dictionary elements via a `kwargs` argument like so: `kwargs={""method"": ""trf""}`. This behaviour contradicts what is mentioned in the docstring.

### What did you expect to happen?

No error thrown

### Minimal Complete Verifiable Example

```Python
import pandas as pd
import xarray as xr
import numpy as np

da = xr.DataArray(

    np.random.rand(4, 3),

    [

        (""time"", pd.date_range(""2000-01-01"", periods=4)),

        (""space"", [""IA"", ""IL"", ""IN""]),

    ],

)
da.curvefit(coords=[""time""], func=lambda x, params: x, method=""trf"")
```


### MVCE confirmation

- [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
- [X] Complete example — the example is self-contained, including all data and the text of any traceback.
- [X] Verifiable example — the example copy & pastes into an IPython prompt or [Binder notebook](https://mybinder.org/v2/gh/pydata/xarray/main?urlpath=lab/tree/doc/examples/blank_template.ipynb), returning the result.
- [X] New issue — a search of GitHub Issues suggests this is not a duplicate.

### Relevant log output

```Python
TypeError: curvefit() got an unexpected keyword argument 'method'
```


### Anything else we need to know?

_No response_

### Environment

<details>
```shell
commit: None
python: 3.8.12 | packaged by conda-forge | (default, Jan 30 2022, 23:42:07)
[GCC 9.4.0]
python-bits: 64
OS: Linux
OS-release: 5.4.0-1061-aws
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: C.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.12.1
libnetcdf: 4.8.1

xarray: 2022.3.0
pandas: 1.4.3
numpy: 1.22.0
scipy: 1.6.2
netCDF4: 1.6.0
pydap: None
h5netcdf: 0.15.0
h5py: 3.7.0
Nio: None
zarr: 2.10.3
cftime: 1.6.1
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: 0.9.10.1
iris: None
bottleneck: None
dask: 2022.03.0
distributed: 2022.3.0
matplotlib: None
cartopy: None
seaborn: None
numbagg: None
fsspec: 2022.01.0
cupy: None
pint: None
sparse: 0.13.0
setuptools: 63.1.0
pip: 22.2.2
conda: None
pytest: 6.2.5
IPython: 8.4.0
sphinx: None
```
</details>
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