Add support for time-base scheduling of blacklists

[laghoule]

My use case:

I have created a blacklist URL of YouTube, and I want to create a schedule for when I want it to block access.

Example of config:

blocking:
  blackLists:
    youtube:
      - https://raw.githubusercontent.com/gieljnssns/Social-media-Blocklists/master/pihole-youtube.txt
  schedules:
    youtube:
      - days: ["Mon", "Tue", "Wed", "Thu"]
        hoursRanges:
          - "06:45-08:30"
          - "19:00-23:30"
      - days: ["Sun"]
        hoursRanges:
          - "20:00-23:30" 

So, I have implemented it, with updated doc, readme & unit-tests. It's working fine on my K8S cluster for 1 month.
Let me know what you think.

Thanks for the project.

[kwitsch]

This looks interesting. 👍

A case I just thought about which could be problematic with the current implementation:

• blocklist has schedule 8 to 17 o'clock
• block TTL is set to 1 hour
• temporary blocked URL is requested at 16.45
• same URL(not blocked anymore) is requested at 16.15

Same applies the other way around(pre and post 8).

This is just a theoretical scenario since such huge TTLs aren't beneficial most of the time(I know some users configure such TTLs tho).
This scenario isn't limited to this change but also applies to disabling blocklists manually.

Best practice in my opinion would be to clear cache entries covered by newly enabled/disabled blocklists.

[laghoule]

@kwitsch Thanks for your feedback, I will look into it.

[codecov]

Codecov Report

Attention: Patch coverage is 83.44828% with 24 lines in your changes missing coverage. Please review.

Project coverage is 93.91%. Comparing base (fe84ab8) to head (05d579a).
Report is 87 commits behind head on main.

❗ Current head 05d579a differs from pull request most recent head 899e005

Please upload reports for the commit 899e005 to get more accurate results.

Files	Patch %	Lines
resolver/blocking_resolver.go	7.69%	10 Missing and 2 partials ⚠️
config/schedules.go	85.18%	6 Missing and 2 partials ⚠️
config/schedule.go	93.93%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1428      +/-   ##
==========================================
+ Coverage   93.88%   93.91%   +0.02%     
==========================================
  Files          78       80       +2     
  Lines        6361     5141    -1220     
==========================================
- Hits         5972     4828    -1144     
+ Misses        300      216      -84     
- Partials       89       97       +8     

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