[IMP] energy_selfconsumption: invoicing integration fixes

Changelog

• [IMP] energy_selfconsumption: validate invoicing mode before activation
• [REF] energy_selfconsumption: renaming method _prepare_contract_template_values
• [IMP] energy_selfconsumption: set company_id on contract creation
• [REF] energy_selfconsumption: remove fields defined in contract.template
• [REF] energy_selfconsumption: using ORM to write name
• [IMP] energy_selfconsumption: set project_id of contract
• [CLN] energy_selfconsumption: remove unused fields
• [REF] energy_selfconsumption: use method to get contract line values
• [FIX] energy_selfconsumption: formula didn't get coefficient
• [IMP] energy_selfconsumption: format name contract line from contract template line
• [FIX] energy_selfconsumption: uom_id didn't set in contract.line
• [IMP] energy_selfconsumption: updated unit testing to integrate invoicing mode