docs: add v10 release notes to NEWS.md

Author: AayushSabharwal

NEWS.md

@@ -1,6 +1,6 @@
 # ModelingToolkit v10 Release Notes
 
-### Callbacks
+## Callbacks
 
 Callback semantics have changed.
 
@@ -17,6 +17,118 @@ event = SymbolicDiscreteCallback(
     [t == 1] => [p ~ Pre(p) + 1], discrete_parameters = [p])
 ```
 
+## New `mtkcompile` and `@mtkcompile`
+
+`structural_simplify` is now renamed to `mtkcompile`. `@mtkbuild` is renamed to
+`@mtkcompile`. Their functionality remains the same. However, instead of a second
+positional argument `structural_simplify(sys, (inputs, outputs))` the inputs and outputs
+should be specified via keyword arguments as `mtkcompile(sys; inputs, outputs, disturbance_inputs)`.
+
+## Reduce reliance on metadata in `mtkcompile`
+
+Previously, `mtkcompile` (formerly `structural_simplify`) used to rely on the metadata of
+symbolic variables to identify variables/parameters/brownians. This was regardless of
+what the system expected the variable to be. Now, it respects the information in the system.
+
+## Unified `System` type
+
+There is now a single common `System` type for all types of models except PDEs, for which
+`PDESystem` still exists. It follows the same syntax as `ODESystem` and `NonlinearSystem`
+did. `System(equations, t[, vars, pars])` will construct a time-dependent system.
+`System(equations[, vars, pars])` will construct a time-independent system. Refer to the
+docstring for `System` for further information.
+
+Utility constructors are defined for:
+
+  - `NonlinearSystem(sys)` to convert a time-dependent system to a time-independent one for
+    its steady state.
+  - `SDESystem(sys, noise_eqs)` to add noise to a system
+  - `JumpSystem(jumps, ...)` to define a system with jumps. Note that normal equations can
+    also be passed to `jumps`.
+  - `OptimizationSystem(cost, ...)` to define a system for optimization.
+
+All problem constructors validate that the system matches the expected structure for
+that problem.
+
+## No more `parameter_dependencies`
+
+The `parameter_dependencies` keyword is deprecated. All equations previously passed here
+should now be provided as part of the standard equations of the system. If passing parameters
+explicitly to the `System` constructor, the dependent parameters (on the left hand side of
+parameter dependencies) should also be provided. These will be separated out when calling
+`complete` or `mtkcompile`. Calling `parameter_dependencies` or `dependent_parameters` now
+requires that the system is completed. The new `SDESystem` constructor still retains the
+`parameter_dependencies` keyword argument since the number of equations has to match the
+number of columns in `noise_eqs`.
+
+ModelingToolkit now has discretion of what parameters are eliminated using the parameter
+equations during `complete` or `mtkcompile`.
+
+## New problem and constructors
+
+Instead of `XProblem(sys, u0map, tspan, pmap)` for time-dependent problems and
+`XProblem(sys, u0map, pmap)` for time-independent problems, the syntax has changed to
+`XProblem(sys, op, tspan)` and `XProblem(sys, op)` respectively. `op` refers to the
+operating point, and is a variable-value mapping containing both unknowns and parameters.
+
+`XFunction` constructors also no longer accept the list of unknowns and parameters as
+positional arguments.
+
+## Removed `DelayParentScope`
+
+The outdated `DelayParentScope` has been removed.
+
+## Removed `XProblemExpr` and `XFunctionExpr`
+
+The old `XProblemExpr` and `XFunctionExpr` constructors used to build an `Expr` that
+constructs `XProblem` and `XFunction` respectively are now removed. This functionality
+is now available by passing `expression = Val{true}` to any problem or function constructor.
+
+## Renaming of `generate_*` and `calculate_*` methods
+
+Several `generate_*` methods have been renamed, along with some `calculate_*` methods.
+The `generate_*` methods also no longer accept a list of unknowns and/or parameters. Refer
+to the documentation for more information.
+
+## New behavior of `getproperty` and `setproperty!`
+
+Using `getproperty` to access fields of a system has been deprecated for a long time, and
+this functionality is now removed. `setproperty!` previously used to update the default
+of the accessed symbolic variable. This is not supported anymore. Defaults can be updated by
+mutating `ModelingToolkit.get_defaults(sys)`.
+
+## New behavior of `@constants`
+
+`@constants` now creates parameters with the `tunable = false` metadata by default.
+
+## Removed `FunctionalAffect`
+
+`FunctionalAffect` is now removed in favor of the new `ImperativeAffect`. Refer to the
+documentation for more information.
+
+## Improved system metadata
+
+Instead of an empty field that can contain arbitrary data, the `System` type stores metadata
+identically to `SymbolicUtils.BasicSymbolic`. Metadata is stored in an immutable dictionary
+keyed by a user-provided `DataType` and containing arbitrary values. `System` supports the
+same `SymbolicUtils.getmetadata` and `SymbolicUtils.setmetadata` API as symbolic variables.
+Refer to the documentation of `System` and the aforementioned functions for more information.
+
+## Moved `connect` and `Connector` to ModelingToolkit
+
+Previously ModelingToolkit used the `connect` function and `Connector` type defined in
+Symbolics.jl. These have now been moved to ModelingToolkit along with the experimental
+state machine API. If you imported them from Symbolics.jl, it is recommended to import from
+ModelingToolkit instead.
+
+## Always wrap with `ParentScope` in `@named`
+
+When creating a system using `@named`, any symbolic quantities passed as keyword arguments
+to the subsystem are wrapped in `ParentScope`. Previously, this would only happen if the
+variable wasn't already wrapped in a `ParentScope`. However, the old behavior had issues
+when passing symbolic quantities down multiple levels of the hierarchy. The `@named` macro
+now always performs this wrapping.
+
 # ModelingToolkit v9 Release Notes
 
 ### Upgrade guide