[IMP] pivot: correctly name periods in pivot table

[pro-odoo]

Task: 3899604

Description:

description of this task, what is implemented and why it is implemented that way.

Task: : TASK_ID

review checklist

• [ ] feature is organized in plugin, or UI components
• [ ] support of duplicate sheet (deep copy)
• [ ] in model/core: ranges are Range object, and can be adapted (adaptRanges)
• [ ] in model/UI: ranges are strings (to show the user)
• [ ] undo-able commands (uses this.history.update)
• [ ] multiuser-able commands (has inverse commands and transformations where needed)
• [ ] new/updated/removed commands are documented
• [ ] exportable in excel
• [ ] translations (_t("qmsdf %s", abc))
• [ ] unit tested
• [ ] clean commented code
• [ ] track breaking changes
• [ ] doc is rebuild (npm run doc)
• [ ] status is correct in Odoo

[robodoo]

[VincentSchippefilt]

robodoo r+

[robodoo]

@pro-odoo @VincentSchippefilt because this PR has multiple commits, I need to know how to merge it:

• merge to merge directly, using the PR as merge commit message
• rebase-merge to rebase and merge, using the PR as merge commit message
• rebase-ff to rebase and fast-forward

[VincentSchippefilt]

robodoo rebase-ff

[robodoo]

Merge method set to rebase and fast-forward.