datasource/*: code a little clean up

src/datasources/db/providerAPI.ts

@@ -1,5 +1,4 @@
 import { DataSource } from 'apollo-datasource';
-import { GraphQLError } from 'graphql';
 import { Connection, getConnection } from 'typeorm';
 import { Provider } from '../../model/Provider';
 
@@ -28,7 +27,7 @@ export class ProviderAPI extends DataSource {
     }
 
     async createProvider (provider: any) {
-        let inserts: any;
+        let inserts: any = null;
         await this.connection.transaction(async (entityManager: any) => {
             inserts = await entityManager.getRepository(Provider)
                 .createQueryBuilder('provider')

src/model/Engagement.ts

@@ -1,4 +1,4 @@
-import { Entity, PrimaryGeneratedColumn, ManyToOne, Column, JoinColumn, JoinTable } from 'typeorm';
+import { Entity, PrimaryGeneratedColumn, ManyToOne, Column, JoinColumn } from 'typeorm';
 import { Participant } from './Participant';
 import { CargoBike } from './CargoBike';
 import { EngagementType } from './EngagementType';

src/model/EquipmentType.ts

@@ -1,4 +1,4 @@
-import { Column, Entity, ManyToMany, OneToMany, PrimaryGeneratedColumn } from 'typeorm';
+import { Column, Entity, ManyToMany, PrimaryGeneratedColumn } from 'typeorm';
 import { CargoBike, Lockable } from './CargoBike';
 
 @Entity()