fix: Reset last integration date on account relinking (backport #125)

[mergify]

• Assume the last integration date is set to "31-10-2024" on Account A
• Now Account A is relinked due to a consent that expires soon. The consent start date is "01-11-2024"
• After relinking, a user tries fetching transactions (consent flow) and ends up with

   'from_date' must be equal or after 'from_date' specified in consent scope
  

• This is because transactions sync picks up from the last integration date which is outside the new consent period

Solution:

• Reset the last integration date on relinking the bank account (updates the existing bank account), so that the following transactions sync picks up from the current active consent start date

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  This is an automatic backport of pull request fix: Reset last integration date on account relinking #125 done by Mergify.