Some `ODESystem` fields such as `metadata` are lost when using the `extend` function

[avinashresearch1]

Minimal Reproducible Example 👇

julia> @named sys1 = ODESystem(Equation[],t, [],[]; metadata = Dict(:a => 2))
Model sys1 with 0 equations
States (0):
Parameters (0):

julia> @named sys2 = ODESystem(Equation[],t, [],[])
Model sys2 with 0 equations
States (0):
Parameters (0):

julia> sys_extend = extend(sys1, sys2)
Model sys1 with 0 equations
States (0):
Parameters (0):

julia> sys_extend.metadata

julia> sys1.metadata
Dict{Symbol, Int64} with 1 entry:
  :a => 2

Expected behavior
One would expect to retain the metadata in the extended system

Environment

[49dc2e85] Calculus v0.5.1
  [0c46a032] DifferentialEquations v7.12.0
⌅ [961ee093] ModelingToolkit v8.75.0
⌃ [16a59e39] ModelingToolkitStandardLibrary v2.3.4
  [2774e3e8] NLsolve v4.5.1
⌃ [1dea7af3] OrdinaryDiffEq v6.70.1
  [91a5bcdd] Plots v1.40.1
  [189a3867] Reexport v1.2.2
  [1bc83da4] SafeTestsets v0.1.0
⌃ [0bca4576] SciMLBase v2.24.0
  [efcf1570] Setfield v1.1.1
⌃ [2efcf032] SymbolicIndexingInterface v0.3.5
  [d1185830] SymbolicUtils v1.5.0
⌃ [0c5d862f] Symbolics v5.17.0
  [3a884ed6] UnPack v1.0.2
  [37e2e46d] LinearAlgebra
  [2f01184e] SparseArrays v1.10.0