Added a meta data table - one-to-one relationship approach

[waterflow80]

Description

In this PR we're attempting to separate the seqcol meta-data from the seqcol entities, by storing them into a separate table.
Fixes #13

Changes made

• Created a separate SeqColMetadata entity
• Made the primary key of the this entity composite of seqcol_digest & naming_convention:
  • I think this should be discussed further to decide whether we should be adding more columns to the primary key, or we should even consider changing the relationship to a one-to-many relationship. It depends on the possible different shapes that a seqcol can take in the future.

Here's the new Java model:

classDiagram
    class SeqColLevelOneEntity
    SeqColLevelOneEntity: - digest
    SeqColLevelOneEntity: - seqColLevel1Object
    class SeqColMetadata
    SeqColMetadata: - seqColDigest
    SeqColMetadata: - sourceIdentifier
    SeqColMetadata: - sourceUrl
    SeqColMetadata: - namingConvention
    SeqColMetadata: - timestamp
    SeqColLevelOneEntity --> SeqColMetadata

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And a sample content of the seqcol_md table:

Changes to make

Each change of the following can be set in a different issue

• Change the return type of the ingestion endpoint in case we have duplicate seqcol with different meta-data.
• Update the ingestion process by including the metadata object as parameter of the construction methods.
• Complete the logic for the source_url & timestamp
• Adding some test cases to cover all possible scenarios.

Discussion

I'm not sure to what extent this approach can cover all the possible scenarios of seqcol meta-data content, and I think making a one-to-many relationship might be efficient in case we had to make all columns of the seqcol_md table primary keys, which means:

• we can have different seqcol with same digest but with different source identifiers &
• we can have different seqcol with same digest and naming convention but with different source identifier &
• we can have different seqcol with same digest, naming convention and source identifier but with different source_url &
• ...

NOTE: The current seqcol_md table have both seqcol_digest & naming_convention as composite primary key, which means that we can't find two seqcol objects with same digest and same naming_convention. Can we get such case ??