diff --git a/packages/strapi-admin/models/Role.settings.json b/packages/strapi-admin/models/Role.settings.json
index b96462c30c..592c5a00e5 100644
--- a/packages/strapi-admin/models/Role.settings.json
+++ b/packages/strapi-admin/models/Role.settings.json
@@ -7,7 +7,7 @@
   "attributes": {
     "name": {
       "type": "string",
-      "minLength": 3,
+      "minLength": 1,
       "unique": true,
       "configurable": false,
       "required": true
diff --git a/packages/strapi-admin/models/User.settings.json b/packages/strapi-admin/models/User.settings.json
index 69888075c1..44db31a58e 100644
--- a/packages/strapi-admin/models/User.settings.json
+++ b/packages/strapi-admin/models/User.settings.json
@@ -8,18 +8,20 @@
     "firstname": {
       "type": "string",
       "unique": false,
+      "minLength": 1,
       "configurable": false,
       "required": false
     },
     "lastname": {
       "type": "string",
       "unique": false,
+      "minLength": 1,
       "configurable": false,
       "required": false
     },
     "username": {
       "type": "string",
-      "unique": true,
+      "unique": false,
       "configurable": false,
       "required": false
     },
diff --git a/packages/strapi-connector-bookshelf/lib/mount-models.js b/packages/strapi-connector-bookshelf/lib/mount-models.js
index d1af995f33..900b7e2b56 100644
--- a/packages/strapi-connector-bookshelf/lib/mount-models.js
+++ b/packages/strapi-connector-bookshelf/lib/mount-models.js
@@ -138,11 +138,7 @@ module.exports = ({ models, target }, ctx) => {
 
       // Exclude polymorphic association.
       if (globalName !== '*') {
-        globalId = details.plugin
-          ? details.plugin === 'admin'
-            ? _.get(strapi.admin, `models.${globalName.toLowerCase()}.globalId`)
-            : _.get(strapi.plugins, `${details.plugin}.models.${globalName.toLowerCase()}.globalId`)
-          : _.get(strapi.models, `${globalName.toLowerCase()}.globalId`);
+        globalId = strapi.db.getModel(globalName.toLowerCase(), details.plugin).globalId;
       }
 
       switch (verbose) {
diff --git a/packages/strapi-database/lib/database-manager.js b/packages/strapi-database/lib/database-manager.js
index 90771ed595..b01e6f996a 100644
--- a/packages/strapi-database/lib/database-manager.js
+++ b/packages/strapi-database/lib/database-manager.js
@@ -120,6 +120,14 @@ class DatabaseManager {
     });
   }
 
+  getModelsByPluginName(pluginName) {
+    if (!pluginName) {
+      return strapi.models;
+    }
+
+    return pluginName === 'admin' ? strapi.admin.models : strapi.plugins[pluginName].models;
+  }
+
   getReservedNames() {
     return {
       models: constants.RESERVED_MODEL_NAMES,
diff --git a/packages/strapi-utils/lib/models.js b/packages/strapi-utils/lib/models.js
index e355677a4b..708a5a78e2 100644
--- a/packages/strapi-utils/lib/models.js
+++ b/packages/strapi-utils/lib/models.js
@@ -38,11 +38,7 @@ module.exports = {
       other: '',
     };
 
-    const models = attribute.plugin
-      ? attribute.plugin === 'admin'
-        ? strapi.admin.models
-        : strapi.plugins[attribute.plugin].models
-      : strapi.models;
+    const models = strapi.db.getModelsByPluginName(attribute.plugin);
 
     const pluginModels = Object.values(strapi.plugins).reduce((acc, plugin) => {
       return acc.concat(Object.values(plugin.models));
@@ -326,15 +322,8 @@ module.exports = {
       });
 
       if (targetName !== '*') {
-        if (association.plugin) {
-          const models =
-            association.plugin === 'admin'
-              ? strapi.admin.models
-              : strapi.plugins[association.plugin].models || {};
-          details = _.get(models, [targetName, 'attributes', association.via]);
-        } else {
-          details = _.get(strapi.models, [targetName, 'attributes', association.via], {});
-        }
+        const models = strapi.db.getModelsByPluginName(association.plugin);
+        details = _.get(models, [targetName, 'attributes', association.via], {});
       }
 
       // Build associations object