[13.0][MIG] website_slides

[Yasaie]

Migration of website_slides

I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

[joshuashort]

I get a similar type of error as I was getting in surveys before trying (#2305) -- in this case, slide.category records don't seem to be migrated to slide.slide?

odoo_1        | 2020-10-01 17:00:54,875 1 ERROR devel odoo.sql_db: bad query: ALTER TABLE "slide_slide" ADD FOREIGN KEY ("category_id") REFERENCES "slide_slide"("id") ON DELETE set null
odoo_1        | ERROR: insert or update on table "slide_slide" violates foreign key constraint "slide_slide_category_id_fkey"
odoo_1        | DETAIL:  Key (category_id)=(3) is not present in table "slide_slide".
odoo_1        |  

[pedrobaeza]

I'm afraid there were a lot of missing pieces, but I have completed them. Let's see the CI result if any query/syntax is misplaced.