Angle parsing should handle Epoch=0 when provided AZ/EL observation

[interplanetarychris]

https://github.com/consensys-space/trusat-orbit/blob/00bf2f2a9f674e03e4b01fbc73fb1bb48e6df494/iod.py#L422

This may also have implications on downstream use of RA/DEC as a default, and instead should operate with the angle as specified, or handle this case by asserting an EPOCH when creating an RA/DEC from an AZ/EL.