Fix OEP full - spin polarized case

Description

The OEP full was not taking the right occupations for the spin-polarized case.

News snippet

The OEP full was not taking the right occupations for the spin-polarized case.

Checklist

• I have checked that my code follows the Octopus coding standards
• I have added tests for all the new features added in this request.

src/classical/charged_particle.F90

@@ -23,6 +23,7 @@ module charged_particle_oct_m
   use classical_particle_oct_m
   use clock_oct_m
   use coulomb_force_oct_m
+  use current_to_mxll_field_oct_m
   use debug_oct_m
   use global_oct_m
   use interaction_oct_m
@@ -110,6 +111,9 @@ contains
     call this%supported_interactions%add(LORENTZ_FORCE)
     call this%supported_interactions%add(COULOMB_FORCE)
     call this%supported_interactions_as_partner%add(COULOMB_FORCE)
+    call this%supported_interactions_as_partner%add(CURRENT_TO_MXLL_FIELD)
+
+    this%quantities(CURRENT)%required = .true.
 
     POP_SUB(charged_particle_init)
   end subroutine charged_particle_init
@@ -180,6 +184,10 @@ contains
       ! The charged particle has a charge, but it is not necessary to update it, as it does not change with time.
       ! We still need to set its clock, so we set it to be in sync with the particle position.
       call this%quantities(iq)%clock%set_time(this%quantities(POSITION)%clock)
+    case(CURRENT)
+      ! The charged particle has a velocity, and the current is directly giving the current.
+      ! We still need to set its clock, so we set it to be in sync with the particle position.
+      call this%quantities(iq)%clock%set_time(this%quantities(VELOCITY)%clock)
     case default
       ! Other quantities should be handled by the parent class
       call this%classical_particle_t%update_quantity(iq)
@@ -202,7 +210,11 @@ contains
       call partner%quantities(iq)%clock%set_time(partner%quantities(POSITION)%clock)
       call multisystem_debug_write_marker(partner%namespace, &
         event_clock_update_t("quantity", QUANTITY_LABEL(iq), partner%quantities(iq)%clock, "set"))
-
+     case (CURRENT)
+      ! We still need to set its clock, so we set it to be in sync with the particle velocity.
+      call partner%quantities(iq)%clock%set_time(partner%quantities(VELOCITY)%clock)
+      call multisystem_debug_write_marker(partner%namespace, &
+        event_clock_update_t("quantity", QUANTITY_LABEL(iq), partner%quantities(iq)%clock, "set"))
     case default
       ! Other quantities should be handled by the parent class
       call partner%classical_particle_t%update_exposed_quantity(iq)
@@ -223,7 +235,12 @@ contains
       interaction%partner_np = 1
       SAFE_ALLOCATE(interaction%partner_charge(1))
       SAFE_ALLOCATE(interaction%partner_pos(1:partner%space%dim, 1))
-
+    type is (current_to_mxll_field_t)
+      interaction%partner_np = 1
+      interaction%grid_based_partner = .false.
+      SAFE_ALLOCATE(interaction%partner_charge(1))
+      SAFE_ALLOCATE(interaction%partner_pos(1:partner%space%dim, 1))
+      SAFE_ALLOCATE(interaction%partner_vel(1:partner%space%dim, 1))
     class default
       ! Other interactions should be handled by the parent class
       call partner%classical_particle_t%init_interaction_as_partner(interaction)
@@ -244,6 +261,11 @@ contains
       interaction%partner_charge(1) = partner%charge(1)
       interaction%partner_pos(:,1) = partner%pos(:, 1)
 
+    type is (current_to_mxll_field_t)
+      interaction%partner_charge(1) = partner%charge(1)
+      interaction%partner_pos(:,1) = partner%pos(:, 1)
+      interaction%partner_vel(:,1) = partner%vel(:, 1)
+
     class default
       call partner%classical_particle_t%copy_quantities_to_interaction(interaction)
     end select