[16.0] Donation new features: Generate a Certificate, Thanks Letter, Summary and recurrency

[brendajfa]

No description provided.

[brendajfa]

@alexis-via

I have added the following modules:

• donation_certificate: allows printing and emailing donation certificates using an ODT document template that can be edited as desired.
• donation_letter: enables sending thank-you letters via email with a default template.
• donation_recurrency: includes a recurrence module that works with a cron to generate recurring donations with a wide range of options.
• donation_summary: allows generating donation summaries between two dates, for a specific donor or all donors; it also has the option to send this summary via mass email."

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