Implement command and parser support for add lesson

[junlong4321]

Resolves #128

[codecov-io]

Codecov Report

Merging #129 into master will increase coverage by 0.51%.
The diff coverage is 92.04%.

@@             Coverage Diff              @@
##             master     #129      +/-   ##
============================================
+ Coverage     79.04%   79.56%   +0.51%     
- Complexity      764      786      +22     
============================================
  Files           122      124       +2     
  Lines          2114     2202      +88     
  Branches        222      232      +10     
============================================
+ Hits           1671     1752      +81     
- Misses          392      393       +1     
- Partials         51       57       +6     

Impacted Files	Coverage Δ	Complexity Δ
...seedu/address/logic/commands/AddLessonCommand.java	86.20% <86.20%> (ø)	10.00 <10.00> (?)
...in/java/seedu/address/logic/parser/ParserUtil.java	94.91% <92.85%> (-1.86%)	17.00 <5.00> (+5.00)	⬇️
...u/address/logic/parser/AddLessonCommandParser.java	95.83% <95.83%> (ø)	5.00 <5.00> (?)
...ain/java/seedu/address/logic/parser/CliSyntax.java	92.30% <100.00%> (+4.80%)	1.00 <0.00> (ø)
...va/seedu/address/logic/parser/TutorsPetParser.java	100.00% <100.00%> (ø)	27.00 <0.00> (+1.00)
...a/seedu/address/model/moduleclass/ModuleClass.java	100.00% <100.00%> (ø)	18.00 <1.00> (+1.00)

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[ypinhsuan]

Looks good! But I think you might need to update the TutorsPetParser class with AddLessonCommand

[dextertanyj]

Awesome work! Just needs to add the AddLessonCommand to TutorsPetParser and everything should be good to go.

[ypinhsuan]

LGTM!

[dextertanyj]

LGTM! Just a minor suggestion for clarity.