Error when using orbit files v2.0

Running a simple simulation with the new orbit files yields an error (see below).

We should

• fix the issue by explicitly converting spacecraft indices from string to int
• prevent the double warning for orbit file development version
• make sure that unit tests capture errors like this

>>> from lisainstrument import Instrument
>>> i = Instrument(orbits='/Users/j2b/Downloads/keplerian-orbits.h5', size=1000)
You are using an orbit file in a development version
You are using an orbit file in a development version
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [2], in <cell line: 1>()
----> 1 i = Instrument(orbits='/Users/j2b/Downloads/keplerian-orbits.h5', size=1000)

File ~/Developer/lisa-simulation/instrument/lisainstrument/instrument.py:337, in Instrument.__init__(self, size, dt, t0, physics_upsampling, aafilter, orbits, orbit_dataset, gws, interpolation, glitches, lock, offsets_freqs, laser_asds, central_freq, modulation_asds, modulation_freqs, tdir_tone, clock_asds, clock_offsets, clock_freqoffsets, clock_freqlindrifts, clock_freqquaddrifts, clockinv_tolerance, clockinv_maxiter, backlink_asds, backlink_fknees, testmass_asds, testmass_fknees, oms_asds, oms_fknees, ttl_coeffs, sc_jitter_asds, mosa_jitter_asds, mosa_angles, dws_asds, ranging_biases, ranging_asds)
    334     self.offsets_freqs = ForEachMOSA(offsets_freqs)
    336 # Orbits, gravitational waves, glitches
--> 337 self.init_orbits(orbits, orbit_dataset)
    338 self.init_gws(gws)
    339 self.init_glitches(glitches)

File ~/Developer/lisa-simulation/instrument/lisainstrument/instrument.py:484, in Instrument.init_orbits(self, orbits, orbit_dataset)
    482     self.init_orbits_file_1_0(orbitf)
    483 elif version in SpecifierSet('== 2.*', True):
--> 484     self.init_orbits_file_2_0(orbitf)
    485 else:
    486     raise ValueError(f"unsupported orbit file version '{version}'")

File ~/Developer/lisa-simulation/instrument/lisainstrument/instrument.py:552, in Instrument.init_orbits_file_2_0(self, orbitf)
    550     else:
    551         dataset = orbitf['tcb/delta_tau']
--> 552         self.tps_proper_time_deviations = ForEachSC(lambda sc: interpolate(dataset[:, sc - 1], self.physics_t))
    553 except ValueError as error:
    554     logger.error("Missing orbit information at \n%s", self.physics_t)

File ~/Developer/lisa-simulation/instrument/lisainstrument/containers.py:31, in ForEachObject.__init__(self, values)
     29     self.dict = {mosa: values[mosa] for mosa in self.indices()}
     30 elif callable(values):
---> 31     self.dict = {mosa: values(mosa) for mosa in self.indices()}
     32 elif isinstance(values, h5py.Dataset):
     33     self.dict = {mosa: values[mosa] for mosa in self.indices()}

File ~/Developer/lisa-simulation/instrument/lisainstrument/containers.py:31, in <dictcomp>(.0)
     29     self.dict = {mosa: values[mosa] for mosa in self.indices()}
     30 elif callable(values):
---> 31     self.dict = {mosa: values(mosa) for mosa in self.indices()}
     32 elif isinstance(values, h5py.Dataset):
     33     self.dict = {mosa: values[mosa] for mosa in self.indices()}

File ~/Developer/lisa-simulation/instrument/lisainstrument/instrument.py:552, in Instrument.init_orbits_file_2_0.<locals>.<lambda>(sc)
    550     else:
    551         dataset = orbitf['tcb/delta_tau']
--> 552         self.tps_proper_time_deviations = ForEachSC(lambda sc: interpolate(dataset[:, sc - 1], self.physics_t))
    553 except ValueError as error:
    554     logger.error("Missing orbit information at \n%s", self.physics_t)

TypeError: unsupported operand type(s) for -: 'str' and 'int'