FINERACT-2517: Upgrade to Postgresql version 18

[nidhiii128]

Description

Describe the changes made and why they were made. (Ignore if these details are present on the associated Apache Fineract JIRA ticket.)

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[IOhacker]

README.md should be updated to it has a reference that minimal version is pg 17

[nidhiii128]

README.md should be updated to it has a reference that minimal version is pg 17

it is already updated to pg 17

[IOhacker]

@nidhiii128 but it has to be postgres >= 18

[nidhiii128]

@nidhiii128 but it has to be postgres >= 18

yeah mb would update it to >=18

[IOhacker]

LGTM