Transformation from ProjString type does not work

[felixcremer]

I thought, that ProjString objects should work similar to plain strings with the proj information, but here it works with strings but fails with ProjString:

julia> equi7_eu_projstring = "+proj=aeqd +lat_0=53 +lon_0=24 +x_0=5837287.81977 +y_0=2121415.69617 +datum=WGS84 +units=m +no_defs"
"+proj=aeqd +lat_0=53 +lon_0=24 +x_0=5837287.81977 +y_0=2121415.69617 +datum=WGS84 +units=m +no_defs"

julia> trans = Proj.Transformation(equi7_eu_projstring, "EPSG:3857", always_xy=true)
Transformation pipeline
    description: Inverse of unknown + axis order change (2D) + Popular Visualisation Pseudo-Mercator
    definition: proj=pipeline step inv proj=aeqd lat_0=53 lon_0=24 x_0=5837287.81977 y_0=2121415.69617 ellps=WGS84 step proj=webmerc lat_0=0 lon_0=0 x_0=0 y_0=0 ellps=WGS84
    direction: forward


julia> trans = Proj.Transformation(ProjString(equi7_eu_projstring), EPSG(3857), always_xy=true)
ERROR: PROJError: proj_create_operations: source_crs is not a CRS

Stacktrace:
 [1] log_func(user_data::Ptr{Nothing}, level::Int32, msg::Cstring)
   @ Proj ~/.julia/packages/Proj/YfK57/src/error.jl:19
 [2] proj_create_crs_to_crs_from_pj (repeats 2 times)
   @ ~/.julia/packages/Proj/YfK57/src/libproj.jl:409 [inlined]
 [3] #Transformation#14
   @ ~/.julia/packages/Proj/YfK57/src/coord.jl:130 [inlined]
 [4] Transformation
   @ ~/.julia/packages/Proj/YfK57/src/coord.jl:122 [inlined]
 [5] Proj.Transformation(source_crs::ProjString, target_crs::EPSG{…}; always_xy::Bool, direction::PJ_DIRECTION, area::Ptr{…}, ctx::Ptr{…})
   @ Proj ~/.julia/packages/Proj/YfK57/src/coord.jl:96
 [6] top-level scope
   @ REPL[76]:1
Some type information was truncated. Use `show(err)` to see complete types.