Small Miscellaneous coil fixes

[dpanici]

• adds setup method for coils, so when loading attributes will be set to None if they do not exist.
• Add default for current
• add missing name to docstring of FourierXYZCoil

[codecov]

Codecov Report

Attention: Patch coverage is 87.50000% with 1 line in your changes missing coverage. Please review.

Project coverage is 95.69%. Comparing base (48eb4d0) to head (58c9b27).
Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
desc/coils.py	87.50%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1311   +/-   ##
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  Coverage   95.69%   95.69%           
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  Files         101      101           
  Lines       25633    25638    +5     
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+ Hits        24529    24534    +5     
  Misses       1104     1104           

Files with missing lines	Coverage Δ
desc/coils.py	97.95% <87.50%> (-0.13%)	⬇️

... and 1 file with indirect coverage changes

[github-actions]

|             benchmark_name             |         dt(%)          |         dt(s)          |        t_new(s)        |        t_old(s)        | 
| -------------------------------------- | ---------------------- | ---------------------- | ---------------------- | ---------------------- |
 test_build_transform_fft_lowres         |     +1.07 +/- 6.60     | +6.10e-03 +/- 3.75e-02 |  5.75e-01 +/- 3.4e-02  |  5.69e-01 +/- 1.6e-02  |
 test_equilibrium_init_medres            |     -0.09 +/- 5.43     | -4.07e-03 +/- 2.43e-01 |  4.47e+00 +/- 1.7e-01  |  4.47e+00 +/- 1.7e-01  |
 test_equilibrium_init_highres           |     -0.81 +/- 4.52     | -4.67e-02 +/- 2.60e-01 |  5.69e+00 +/- 2.0e-01  |  5.74e+00 +/- 1.6e-01  |
 test_objective_compile_dshape_current   |     +1.00 +/- 4.93     | +4.24e-02 +/- 2.10e-01 |  4.30e+00 +/- 1.2e-01  |  4.25e+00 +/- 1.7e-01  |
 test_objective_compute_dshape_current   |     -0.47 +/- 2.43     | -2.49e-05 +/- 1.28e-04 |  5.26e-03 +/- 8.6e-05  |  5.28e-03 +/- 9.6e-05  |
 test_objective_jac_dshape_current       |     +0.60 +/- 6.57     | +2.59e-04 +/- 2.87e-03 |  4.38e-02 +/- 1.5e-03  |  4.36e-02 +/- 2.4e-03  |
 test_perturb_2                          |     -0.80 +/- 1.52     | -1.66e-01 +/- 3.14e-01 |  2.05e+01 +/- 2.4e-01  |  2.06e+01 +/- 2.0e-01  |
 test_proximal_freeb_jac                 |     +0.86 +/- 2.07     | +6.48e-02 +/- 1.55e-01 |  7.55e+00 +/- 1.4e-01  |  7.49e+00 +/- 5.7e-02  |
 test_solve_fixed_iter                   |     -0.52 +/- 2.44     | -1.74e-01 +/- 8.09e-01 |  3.29e+01 +/- 6.1e-01  |  3.31e+01 +/- 5.3e-01  |
 test_LinearConstraintProjection_build   |     +0.49 +/- 3.01     | +5.26e-02 +/- 3.21e-01 |  1.07e+01 +/- 2.4e-01  |  1.07e+01 +/- 2.1e-01  |
 test_build_transform_fft_midres         |     +0.40 +/- 1.75     | +2.41e-03 +/- 1.06e-02 |  6.07e-01 +/- 8.0e-03  |  6.04e-01 +/- 6.9e-03  |
 test_build_transform_fft_highres        |     +1.71 +/- 6.20     | +1.66e-02 +/- 6.03e-02 |  9.88e-01 +/- 6.0e-02  |  9.72e-01 +/- 7.0e-03  |
 test_equilibrium_init_lowres            |     -0.07 +/- 2.04     | -2.56e-03 +/- 7.85e-02 |  3.85e+00 +/- 5.9e-02  |  3.85e+00 +/- 5.2e-02  |
 test_objective_compile_atf              |     +1.22 +/- 3.37     | +1.02e-01 +/- 2.80e-01 |  8.41e+00 +/- 1.3e-01  |  8.31e+00 +/- 2.5e-01  |
 test_objective_compute_atf              |     +0.04 +/- 1.78     | +6.61e-06 +/- 2.80e-04 |  1.57e-02 +/- 2.3e-04  |  1.57e-02 +/- 1.6e-04  |
 test_objective_jac_atf                  |     +0.14 +/- 5.01     | +2.80e-03 +/- 9.93e-02 |  1.98e+00 +/- 5.8e-02  |  1.98e+00 +/- 8.1e-02  |
 test_perturb_1                          |     +0.01 +/- 1.53     | +1.78e-03 +/- 2.25e-01 |  1.47e+01 +/- 1.0e-01  |  1.47e+01 +/- 2.0e-01  |
 test_proximal_jac_atf                   |     +0.85 +/- 1.87     | +7.01e-02 +/- 1.55e-01 |  8.36e+00 +/- 1.2e-01  |  8.29e+00 +/- 9.7e-02  |
 test_proximal_freeb_compute             |     +0.57 +/- 0.97     | +1.14e-03 +/- 1.93e-03 |  2.01e-01 +/- 1.1e-03  |  2.00e-01 +/- 1.6e-03  |
 test_solve_fixed_iter_compiled          |     +0.03 +/- 1.13     | +6.75e-03 +/- 2.34e-01 |  2.07e+01 +/- 1.5e-01  |  2.07e+01 +/- 1.8e-01  |

[dpanici]

This might not be needed once we decide on #1169 actually, if we have some sort of nfilaments thing there...

[dpanici]

Better to do a subclass of curve instead of coil for stuff like Rogowski etc

[ddudt]

What is the purpose of this? Wouldn't this prevent someone from setting the current to 0, since 0 = False and so it would get replaced with the default value of 1?

[ddudt]

I think you might have meant to do new = setdefault(new, 1)

[ddudt]

Why delete this? I think it should still say Name for this coil. like we have for all the similar methods of other coil classes.

[ddudt]

I prefer proper punctuation in our doc strings, I think we do that in most cases