Rewrite salesforce triggers to make them follow best practices

REQUIREMENTS Need to write triggers in order to be sure that: 1- in the ACCOUNT object, the first_contact__c field (lookup field to CONTACT) points always to the oldest CONTACT associated to the ACCOUNT 2- in the CONTACT object, the source_campaign__c field (lookup field to CAMPAIGN) points always to the oldest CAMPAIGN associated to the CONTACT (i.e. the first CAMPAIGN for which the CONTACT became CAMPAIGN_MEMBER). 3- in the LEAD object, the source_campaign__c field (lookup field to CAMPAIGN) points always to the oldest CAMPAIGN associated to the LEAD (i.e. the first CAMPAIGN for which the LEAD became CAMPAIGN_MEMBER). All of these triggers will have to work with bulk changes and be fully tested. TRIGGER CLASSES TO BE REVIEWED Update lead campaign Update account Update first contact field Update source campaign Update source campaign of contact Update source campaign of lead TEST CLASSES TO BE REVIEWED UpdateAccountTest UpdateSourceCampaignOfContactTest UpdateSourceCampaignOfLeadTest OTHER ITEMS - TO BE REMOVED CAMPAIGN_MEMBER OBJECT. CUSTOM FIELD: Contact_Flag__c CAMPAIGN_MEMBER OBJECT. WF RULE: Update Contact Flag + FIELD UPDATE: Contact Flag