throw an exception if DSN is not set

[marandaneto]

📢 Type of change

• Bugfix
• New feature
• Enhancement
• Refactoring

📜 Description

throw an exception if DSN is not set.

💡 Motivation and Context

if DSN is not set, user needs to know right away, it might be a misconfiguration.

💚 How did you test it?

📝 Checklist

• I reviewed submitted code
• I added tests to verify changes
• All tests passing

🔮 Next steps

[codecov-io]

Codecov Report

Merging #200 into master will decrease coverage by <.01%.
The diff coverage is 0%.

@@ Coverage Diff @@## master #200 +/- ##
============================================
- Coverage 57.94% 57.94% -0.01% - Complexity 547 548 +1 
============================================
Files 72 72 Lines 2611 2613 +2 Branches 227 228 +1 ============================================
+ Hits 1513 1514 +1 - Misses 981 983 +2 + Partials 117 116 -1

Impacted Files	Coverage Δ	Complexity Δ
...ntry-core/src/main/java/io/sentry/core/Sentry.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...c/main/java/io/sentry/core/DirectoryProcessor.java	74.07% <0%> (+3.7%)	7% <0%> (+1%)	⬆️

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[bruno-garcia]

One suggestion