v8.9.0

ModelingToolkit v8.9.0

Diff since v8.8.1

Closed issues:

• convert_system(ODESystem, sys, independent_variable(sys2) gives ArgumentError: Cannot find the parent of ... (#1281)
• sol[u] not working with NonlinearProblem (#1504)
• Optimization readme example not working (#1542)
• ExtraEquationsSystemException - worked in 8.5.5 - related to #1539 and #1537? (#1544)
• Acausal circuit example output doesn't match docs (#1545)
• Calculating nullspace after bareiss! (#1551)

Merged pull requests:

• isisomorphic and convert_system fix (#1543) (@anandijain)
• 📝 update docs for acausal circuit example (#1546) (@AnasAbdelR)
• Promote to concrete type by default if it's an array (#1548) (@YingboMa)
• Scalarize in observed function building (#1549) (@YingboMa)
• rm upstreamed dispatch (#1550) (@anandijain)
• Add nullspace computation (#1552) (@YingboMa)