Add unit tests for Port and Node base classes

[mikejturner]

• Adds unit tests for Port and Node base classes.

• Makes a few small improvements to Port and Node (these are noted in the Changelog file):

  • Trying to add a port to a model with import/export contraints set to FlowConstraint.Series or FlowConstraint.InRange now raises a NotImplementedError.
  • When setting active periods on a Port, the set_active_periods_from_array method now accepts a list of booleans in addition to a list of 0's and 1's.
  • The get_port method on Node now returns None rather than raising a ValueError, if no such port with that name can be found.
  • verify_node now called when adding nodes to models and verify_node modified to now verify not only check the node but also verify (via call to verify_port) any ports attached to the node.

[mikejturner]

✅ Code coverage on improve-unit-tests is at 82% (compared to main being at 82%)

🎉 No files have reduced coverage 🎉

Full Coverage Report

File	Details
src/echo/__init__.py	✅ 100% → 100%
src/echo/configuration.py	✅ 100% → 100%
src/echo/constants.py	✅ 100% → 100%
src/echo/exceptions.py	✅ 88% → 88%
src/echo/functional.py	✅ 100% → 100%
src/echo/models/__init__.py	✅ 100% → 100%
src/echo/models/agnostic/__init__.py	✅ 100% → 100%
src/echo/models/agnostic/aggregation.py	✅ 95% → 95%
src/echo/models/agnostic/base.py	✅ 96% → 96%
src/echo/models/agnostic/bounded.py	✅ 100% → 100%
src/echo/models/agnostic/controlled.py	✅ 100% → 100%
src/echo/models/agnostic/flex.py	✅ 100% → 100%
src/echo/models/agnostic/input_output.py	✅ 100% → 100%
src/echo/models/agnostic/storage.py	✅ 82% → 82%
src/echo/models/agnostic/tellegen/__init__.py	✅ 100% → 100%
src/echo/models/agnostic/tellegen/base.py	✅ 100% → 100%
src/echo/models/agnostic/tellegen/multi_commodity.py	✅ 38% → 38%
src/echo/models/agnostic/tellegen/partitioned_multi_commodity.py	✅ 96% → 96%
src/echo/models/agnostic/tellegen/three_way_valve.py	✅ 90% → 90%
src/echo/models/agnostic/time_delay.py	✅ 100% → 100%
src/echo/models/agnostic/time_varying.py	✅ 76% → 76%
src/echo/models/base/__init__.py	✅ 100% → 100%
src/echo/models/base/base_model.py	✅ 100% → 100%
src/echo/models/base/edge.py	✅ 69% → 69%
src/echo/models/base/node.py	✅ 86% → 98%
src/echo/models/base/optimisation_graph.py	✅ 76% → 76%
src/echo/models/base/path.py	✅ 92% → 92%
src/echo/models/base/port.py	✅ 96% → 98%
src/echo/models/base/transform.py	✅ 90% → 90%
src/echo/models/base/types.py	✅ 100% → 100%
src/echo/models/carbon/__init__.py	✅ 100% → 100%
src/echo/models/carbon/aggregation.py	✅ 100% → 100%
src/echo/models/carbon/base.py	✅ 100% → 100%
src/echo/models/electrical/__init__.py	✅ 100% → 100%
src/echo/models/electrical/base.py	✅ 100% → 100%
src/echo/models/electrical/ev/__init__.py	✅ 100% → 100%
src/echo/models/electrical/ev/base.py	✅ 94% → 94%
src/echo/models/electrical/ev/deprecated.py	✅ 33% → 33%
src/echo/models/electrical/ev/ev_with_profile.py	✅ 68% → 68%
src/echo/models/electrical/ev/v0g.py	✅ 100% → 100%
src/echo/models/electrical/ev/v1g.py	✅ 100% → 100%
src/echo/models/electrical/ev/v2g.py	✅ 100% → 100%
src/echo/models/electrical/generation.py	✅ 94% → 94%
src/echo/models/electrical/inverter.py	✅ 92% → 92%
src/echo/models/gas/__init__.py	✅ 100% → 100%
src/echo/models/gas/base.py	✅ 100% → 100%
src/echo/models/gas/boiler_fixedcop.py	✅ 86% → 86%
src/echo/models/gas/boiler_tempcontrolled.py	✅ 62% → 62%
src/echo/models/prebuilt/__init__.py	✅ 100% → 100%
src/echo/models/prebuilt/battery.py	✅ 71% → 71%
src/echo/models/prebuilt/diesel_generator.py	✅ 45% → 45%
src/echo/models/prebuilt/flex.py	✅ 79% → 79%
src/echo/models/prebuilt/load.py	✅ 91% → 91%
src/echo/models/prebuilt/scaled_solar.py	✅ 67% → 67%
src/echo/models/prebuilt/solar.py	✅ 50% → 50%
src/echo/models/scenario.py	✅ 100% → 100%
src/echo/models/thermal/__init__.py	✅ 100% → 100%
src/echo/models/thermal/base.py	✅ 0% → 0%
src/echo/models/thermal/parameterised_chiller.py	✅ 85% → 85%
src/echo/models/thermal/parameterised_heatpump.py	✅ 88% → 88%
src/echo/models/thermal/simple_chiller.py	✅ 85% → 85%
src/echo/models/thermal/simple_heatpump.py	✅ 92% → 92%
src/echo/models/thermal/simple_heatpump_dualoutput.py	✅ 92% → 92%
src/echo/models/thermal/storage.py	✅ 78% → 78%
src/echo/objectives/__init__.py	✅ 100% → 100%
src/echo/objectives/base.py	✅ 98% → 98%
src/echo/objectives/contingency.py	✅ 93% → 93%
src/echo/objectives/power.py	✅ 86% → 86%
src/echo/objectives/tariff.py	✅ 80% → 80%
src/echo/optimiser.py	✅ 73% → 73%
src/echo/tracker.py	✅ 43% → 43%
src/echo/utils.py	✅ 61% → 61%
src/echo/validators.py	✅ 89% → 91%
src/echo/visualization.py	✅ 91% → 91%
TOTAL	✅ 82% → 82%