Cannot load `MatrixGroup` serialized before renaming

**Describe the bug** #5704 introduced a renaming of `MatrixGroup` and `MatrixGroupElem` but those were serialized type; meaning that anything of this type serialized before this PR does not seem to be loadable anymore. **To Reproduce** So this is experimental code, but I guess it generalizes ``` using Oscar julia> c=get_db()["LeechPairs"]; julia> collect(find(c)) ``` This returns an error that basically tells you ``` ┌ Warning: Attempted loading file stored using a DEV version with commit d34bde84323267444e96b255713bd56c2a6b8437 └ @ Oscar.Serialization ~/.julia/dev/Oscar/src/Serialization/main.jl:867 ERROR: unsupported type 'MatrixGroup' for decoding ``` **Expected behavior** It should load. The solution is to provide an upgrade script. Note that this bugs in dev and in the current release since the PR predates 1.7.0 **System (please complete the following information):** DEV ``` OSCAR version 1.8.0-DEV - #sm/classifying_group_primitive_extensions, 66f1d88c79 -- 2026-03-19 15:29:13 +0100 combining: AbstractAlgebra.jl v0.48.5 GAP.jl v0.16.4 Hecke.jl v0.39.14 Nemo.jl v0.54.1 Polymake.jl v0.13.9 Singular.jl v0.28.8 building on: FLINT_jll v301.400.1+0 GAP_jll v400.1500.101+0 GAP_lib_jll v400.1500.100+0 Singular_jll v404.101.505+3 libpolymake_julia_jll v0.14.6+1 libsingular_julia_jll v0.47.12+1 polymake_jll v400.1500.2+0 polymake_oscarnumber_jll v0.3.16+0 See `]st -m` for a full list of dependencies. Julia Version 1.12.5 Commit 5fe89b8ddc1 (2026-02-09 16:05 UTC) Build Info: Official https://julialang.org release Platform Info: OS: Linux (x86_64-linux-gnu) CPU: 14 × Intel(R) Core(TM) Ultra 5 235U WORD_SIZE: 64 LLVM: libLLVM-18.1.7 (ORCJIT, goldmont) GC: Built with stock GC Threads: 1 default, 1 interactive, 1 GC (on 14 virtual cores) Official https://julialang.org release ``` "stable" ``` OSCAR version 1.7.0 combining: AbstractAlgebra.jl v0.48.5 GAP.jl v0.16.4 Hecke.jl v0.39.14 Nemo.jl v0.54.1 Polymake.jl v0.13.9 Singular.jl v0.28.8 building on: FLINT_jll v301.400.1+0 GAP_jll v400.1500.101+0 GAP_lib_jll v400.1500.100+0 Singular_jll v404.101.505+3 libpolymake_julia_jll v0.14.6+1 libsingular_julia_jll v0.47.12+1 polymake_jll v400.1500.2+0 polymake_oscarnumber_jll v0.3.16+0 See `]st -m` for a full list of dependencies. Julia Version 1.12.5 Commit 5fe89b8ddc1 (2026-02-09 16:05 UTC) Build Info: Official https://julialang.org release Platform Info: OS: Linux (x86_64-linux-gnu) CPU: 14 × Intel(R) Core(TM) Ultra 5 235U WORD_SIZE: 64 LLVM: libLLVM-18.1.7 (ORCJIT, goldmont) GC: Built with stock GC Threads: 1 default, 1 interactive, 1 GC (on 14 virtual cores) Official https://julialang.org release ```