[FIX] mass_mailing: review colors in snippets

* Trig default ".btn.btn-link" rather than custom ".o_mail_link" (not
used anymore)
* Define variations when a button is inside bg-beta or bg-delta

addons/mass_mailing/static/src/less/themes/theme_airmail.less

@@ -15,15 +15,6 @@
     // ===== Colors =====
     .bg-beta {
         background-color: @o_mm_airmail_color_gamma;
-
-        .btn.btn-primary {
-            color: @o_mm_airmail_color_beta;
-            background-color: @o_mm_airmail_color_zeta;
-        }
-
-        h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
-            color: @o_mm_airmail_color_beta;
-        }
     }
     .text-beta {
         color: @o_mm_airmail_color_gamma;
@@ -57,9 +48,23 @@
             background-color: @o_mm_airmail_color_gamma;
         }
 
-        a, .o_mail_link {
+        a, .btn.btn-link {
             color: @o_mm_airmail_color_delta;
         }
+
+        .bg-beta, .bg-delta {
+            h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
+                color: @o_mm_airmail_color_beta;
+            }
+        }
+
+        .bg-beta {
+            .btn.btn-primary {
+                color: @o_mm_airmail_color_delta;
+                background-color: @o_mm_airmail_color_beta;
+                font-weight: bold;
+            }
+        }
     }
 
     // ===== Snippets (specific) =====

addons/mass_mailing/static/src/less/themes/theme_default.less

@@ -35,10 +35,6 @@
 .bg-beta {
     background-color: @o_mm_def_color_zeta;
     color:  @o_mm_def_color_beta;
-
-    h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
-        color: @o_mm_def_color_beta;
-    }
 }
 .text-beta {
     color: @o_mm_def_color_zeta;
@@ -112,6 +108,20 @@
         height: 2px;
         background-color: @o_mm_def_color_alpha;
     }
+
+    .bg-beta {
+        h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
+            color: @o_mm_def_color_beta;
+        }
+
+        .btn.btn-primary {
+            background-color: @o_mm_def_color_eta;
+        }
+
+        a, .btn.btn-link {
+            color: @o_mm_def_color_eta;
+        }
+    }
 }
 
 // ===== Snippets (specific) =====

addons/mass_mailing/static/src/less/themes/theme_newsletter.less

@@ -34,5 +34,15 @@
         a, .btn.btn-link {
             color: @o_mm_news_color_epsilon;
         }
+
+        .bg-delta {
+            .btn.btn-primary {
+                color: @o_mm_news_color_beta;
+                background-color:  @o_mm_news_color_zeta;
+            }
+            a, .btn.btn-link {
+                color: @o_mm_news_color_zeta;
+            }
+        }
     }
 }

addons/mass_mailing/static/src/less/themes/theme_resto.less

@@ -21,10 +21,6 @@
     .bg-beta {
         background-color: @o_mm_resto_color_zeta;
         color: @o_mm_resto_color_beta;
-
-        h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
-            color: @o_mm_resto_color_beta;
-        }
     }
     .text-beta {
         color: @o_mm_resto_color_zeta;
@@ -32,10 +28,6 @@
     .bg-delta {
         background-color: @o_mm_resto_color_gamma;
         color: @o_mm_resto_color_beta;
-
-        h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
-            color: @o_mm_resto_color_beta;
-        }
     }
     .text-delta {
         color: @o_mm_resto_color_epsilon;
@@ -62,7 +54,7 @@
             background-color: @o_mm_resto_color_gamma;
         }
 
-        a, .o_mail_link {
+        a, .btn.btn-link {
             font-weight: normal;
             color: @o_mm_resto_color_epsilon;
         }
@@ -70,6 +62,26 @@
         .separator {
             background-color: lighten(@o_mm_resto_color_zeta, 20%);
         }
+
+        .bg-beta, .bg-delta {
+            h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
+                color: @o_mm_resto_color_beta;
+            }
+        }
+
+        .bg-delta {
+            background-color: @o_mm_resto_color_gamma;
+            color: @o_mm_resto_color_beta;
+
+            a, .btn.btn-link {
+                color: @o_mm_resto_color_zeta;
+            }
+
+            .btn.btn-primary {
+                color: @o_mm_resto_color_beta;
+                background-color: @o_mm_resto_color_zeta;
+            }
+        }
     }
 
     h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {

addons/mass_mailing/static/src/less/themes/theme_tech.less

@@ -17,8 +17,8 @@
         background-color: @o_mm_tech_color_gamma;
 
         .btn.btn-primary {
-            color: @o_mm_tech_color_beta;
-            background-color: @o_mm_tech_color_zeta;
+            color: @o_mm_tech_color_gamma;
+            background-color: @o_mm_tech_color_beta;
         }
     }
     .text-beta {
@@ -51,7 +51,7 @@
             padding-right: 20px;
         }
 
-        a, .o_mail_link {
+        a, .btn.btn-link {
             font-weight: normal;
             color: @o_mm_tech_color_gamma;
         }
@@ -59,6 +59,19 @@
         h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
             color: darken(@o_mm_tech_color_beta, 10%);
         }
+
+        .bg-beta, .bg-delta {
+            h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
+                color: @o_mm_tech_color_beta;
+            }
+        }
+
+        .bg-beta {
+            .btn.btn-primary {
+                color: @o_mm_tech_color_gamma;
+                background-color: @o_mm_tech_color_beta;
+            }
+        }
     }
 
     // ===== Snippets (specific) =====