WIP: Feature/new ic condition2

What this MR does / why does DuMux need it: This MR implements new coupling conditions for stokes-darcy interfaces, as proposed/described by Elissa Eggenweiler. The new interface conditions are meant to be more general and appropriate in comparison to the Beavers-Joseph condition and the current normal momentum coupling.

TODO:

• Combine new/standardPorousMediumVelocity, beaversJoseph/nTangentialVelocity and old/newMomentumCouplingCondition
• Allow unsymmetrizedStressTensorForBJ and unsymmetrizedStressTensorForIC!
• Set up two tests: Beaver-Josephs and newIC, see: dumux/test/multidomain/boundary/stokesdarcy/1p_1p, @Elissa
• Check deprecation and documentation, link to paper from Elissa?
• Add warning for newIC with symmetrized tensor
• Folder and file names should not contain capital letters.
• Follow styleguide: Correct indent, curly braces
• Small TODOs in project

Special notes for your reviewer: I appreciate all help regarding the technicalities of the merge request.

dumux/discretization/staggered/freeflow/boundarytypes.hh

@@ -54,7 +54,7 @@ public:
 
         boundaryInfo_[eqIdx].visited = false;
         boundaryInfo_[eqIdx].isSymmetry = false;
-        boundaryInfo_[eqIdx].isBeaversJoseph = false;
+        boundaryInfo_[eqIdx].isSlipCondition = false;
     }
 
     /*!
@@ -94,34 +94,67 @@ public:
         static_assert(AlwaysFalse<T>::value, "Setting all boundary types to Neumann not permitted!");
     }
 
+    // TODO: deprecate!
     /*!
      * \brief Set a boundary condition for a single equation to
      *        Beavers-Joseph(-Saffmann) (special case of Dirichlet b.c.).
      */
+    [[deprecated("This method will be removed after release (3.n). Use setSlipCondition instead!")]]
     void setBeaversJoseph(unsigned eqIdx)
+    {
+        setSlipCondition(eqIdx);
+    }
+    /*!
+     * \brief Set a boundary condition for a single equation to
+     *        slip condition: bjs,bj or the new one by Elissa Eggenweiler
+     */
+    void setSlipCondition(unsigned eqIdx)
     {
         resetEq(eqIdx);
         boundaryInfo_[eqIdx].visited = true;
-        boundaryInfo_[eqIdx].isBeaversJoseph = true;
+        boundaryInfo_[eqIdx].isSlipCondition = true;
     }
 
+
+    // TODO: Deprecate/Remove? Where used?
     /*!
      * \brief Returns true if an equation is used to specify a
      *        Beavers-Joseph(-Saffman) boundary condition.
      *
      * \param eqIdx The index of the equation
      */
+    [[deprecated("This method will be removed after release (3.n). Use isSlipCondition instead!")]]
     bool isBeaversJoseph(unsigned eqIdx) const
-    { return boundaryInfo_[eqIdx].isBeaversJoseph; }
+    { return isSlipCondition(eqIdx); }
+
+    /*!
+     * \brief Returns true if an equation is used to specify a
+     *        slip condition
+     *
+     * \param eqIdx The index of the equation
+     */
+    bool isSlipCondition(unsigned eqIdx) const
+    { return boundaryInfo_[eqIdx].isSlipCondition; }
 
+    // TODO: Deprecate/Remove? Where used?
     /*!
      * \brief Returns true if some equation is used to specify a
      *        Beavers-Joseph(-Saffman) boundary condition.
      */
+    [[deprecated("This method will be removed after release (3.n). Use hasSlipCondition instead!")]]
     bool hasBeaversJoseph() const
+    {
+        return hasSlipCondition();
+    }
+
+    /*!
+     * \brief Returns true if some equation is used to specify a
+     *        slip condition
+     */
+    bool hasSlipCondition() const
     {
         for (int i = 0; i < numEq; ++i)
-            if (boundaryInfo_[i].isBeaversJoseph)
+            if (boundaryInfo_[i].isSlipCondition)
                 return true;
         return false;
     }
@@ -131,7 +164,7 @@ protected:
     {
         bool visited;
         bool isSymmetry;
-        bool isBeaversJoseph;
+        bool isSlipCondition;
     };
 
     std::array<StaggeredFreeFlowBoundaryInfo, numEq> boundaryInfo_;